Building your own PC might sound intimidating — but if you're a gamer, we know the thought has crossed your mind at least once. After all, a custom-built gaming rig is the only surefire way to get exactly what you want, exactly the way you want it. When you control everything that goes into your PC from the power supply up, you know that you'll be able to play the games you want, at the framerates you want, without sacrificing performance. Building your own PC is easier than you think (not to mention fun and rewarding). It's also the perfect next step if you're already a gamer, because a home-built PC lets you keep the door open for upgrades — as technology changes, as your gaming tastes and needs change, or as your budget allows.
Building a gaming PC isn't difficult, but it's also not always intuitive. That's why we've put together this comprehensive step-by-step guide to building your first gaming PC — complete with tips and tricks from our veteran builders.
PREP 1: PC Build Tools
You will need a large surface to work on, such as a table. To prevent an accidental electrostatic discharge (which can damage sensitive components), make sure you stand on an uncarpeted surface.
You will need a Phillips #2 screwdriver for just about everything.
Optional: If you're installing an M.2 device, you'll need a Phillips #0 screwdriver.
Pro-tip: Magnetic screwdrivers will prevent you from dropping screws inside your case (the magnetic tip is very weak and shouldn't have any effect on your components).
Most components come with additional parts; some optional, some required for installation in your build. You'll need a way to keep assorted screws, zip ties, cables, manuals, etc. organized by individual component — without proper organization, these items can be easily mixed up.
Pro-tip: For assorted screws, we recommend magnetic hardware trays or trays with multiple small compartments such as empty egg cartons or vitamin containers.
Build in a well-lit area with multiple light sources — you don't want to have to worry about blocking your only light source when you bend over the chassis.
Pro-tip: A movable light source will help you illuminate the nooks and crannies of your case. The ideal option is a headlamp, because it leaves your hands free, but you can also use a flashlight, your phone, or a desk lamp.
Anti-Static Wrist Strap
Not strictly necessary, but useful to ensure you don't accidentally damage sensitive components with electrostatic discharge. (This isn't a very common occurrence, but it's better to be safe — and anti-static straps are cheap.)
Not strictly necessary, but tying your cables together will make the inside of your PC look much better. If you don't want to buy zip ties, you can neaten things up with twist-ties (you'll have a bunch from your components' wiring). You can also use Velcro straps — some cases have them integrated.
For cutting zip ties and unpacking components.
PREP 2: Gaming PC Cases
Before you start picking out components, you should have a case — or, at least, a case size — in mind.
The main thing to keep in mind when picking a case is where you're going to put the computer. Your PC's final location will dictate how big you can (or cannot) go, and it will also help determine whether various premium case features are worth splurging on — you probably don't want to pay for a tempered glass side panel if the computer will be hidden under your desk.
Cases typically come in three sizes: Full-tower, mid-tower, and mini-tower. These are very general categories (case sizes are not standardized among manufacturers), but they're based on motherboard size: Full-tower cases are designed to fit both Extended-ATX motherboards and standard full-size ATX motherboards; mid-tower cases are designed to fit standard full-size ATX motherboards; and mini-tower cases are designed to fit a number of smaller motherboards, such as mini-ITX motherboards.
Generally speaking, mid-tower is the most common case size. Mid-tower case dimensions can vary quite a bit, but these cases usually measure around 18 - 20 inches tall, 17 - 20 inches long, and 6 - 8 inches wide. Mid-tower cases are usually roomy enough for a gaming setup with a couple of graphics cards, several hard drives, and a modest cooling system.
Full-tower cases are larger than mid-tower cases — they usually measure around 22 - 24 inches tall, 18 - 20 inches long, and more than 8 inches wide. You'll most likely need a full-tower case if you want to use an Extended-ATX motherboard (although select mid-tower cases do fit Extended-ATX motherboards), or if you want to put in an extensive cooling system or additional storage.
Mini-towers, or small form factor (SFF) builds, are designed to be compact. While SFF builds have come a long way in the last few generations, mini-towers — specifically those using mini-ITX motherboards — require you to carefully plan components (you may need to use components that are specifically made for small builds, such as half-length GPUs) and cooling, and leave little room for upgrading once the build is finished. For this reason, we don't advocate SFF builds for new builders, but they can be a fun challenge if you've already got a build or two under your belt.
Once you figure out how big you want to go, look for a case that's close to that size. If you're not set on a specific size, it's better to err on the larger side — bigger cases are easier to work with and you'll have an easier time upgrading your PC in the future. That said, while a little bigger is good, significantly bigger isn't necessarily better: Large cases can end up with hotspots if not properly cooled.
All case sizes are available at different price points, so finding a case that fits your budget shouldn't be difficult. More expensive cases may have premium and convenience features such as noise dampening, higher-quality build materials, removable drive cages, and more attractive cable management, but these features typically won't noticeably affect performance.
PREP 3: Gaming PC Part
Now it's time to get your components together. This step can be as hands-on or as hands-off as you like — you can thoroughly research each individual component on your own and create a custom build from scratch, or you can find a pre-made build online and adjust it to suit your specific budget and needs.
We definitely recommend coming up with a budget before you start picking components (it's easy for component shopping to get out of hand) — and remember, you can always upgrade individual components later.
Pro-tip: Make a build list before you make any purchases — all components need to be compatible with all other components.
Pro-tip: If you're building this PC because you want to play a certain game, check that game's recommended system requirements and plan accordingly.
Here are the hardware components you need to build a gaming PC:
- Central processing unit (CPU)
- Motherboard — aka, mobo or mainboard
- Memory (RAM)
- Graphics processing unit (GPU) — aka, graphics card
- Storage — SSD and/or HDD
- Power supply unit (PSU)
- System cooling — CPU cooling and chassis airflow
- Gaming peripherals (keyboard, mouse, headphones)
- Operating system
Let's take a look at what each component does, why it's necessary, and what you need to look for while shopping around.
Central Processing Unit (CPU)
The Central Processing Unit (CPU), also known as the processor, is basically the brain of your PC. This is where the magic happens — when a computer program runs, it sends a list of instructions (which are actually more like tasks) to the CPU. The CPU performs each "instruction" and sends signals to other components to let them know when they need to perform a task.
There are two main performance metrics associated with CPUs: Core count and clock speed. Core count tells us how many processors the CPU has — in other words, how many tasks the CPU can perform simultaneously — while clock speed tells us how quickly the CPU is performing each task. Some higher-end CPUs feature hyper-threading, which allows each core to run multiple threads and offers improved performance on threaded software.
Pro-tip: Most modern CPUs are multi-core and many modern games are designed to take advantage of this, so you should look for a CPU with at least four cores. Additional cores can be helpful as you start layering on more tasks, such as recording and streaming your gameplay.
The motherboard is the main circuit board and is connected to everything. The CPU sits directly on the motherboard (your CPU and motherboard must be compatible — Intel® Desktop Compatibility Tool can help) and every other component — graphics cards, hard drives, memory, optical drives, wireless cards — integrates into the motherboard.
Motherboards come in a few different sizes. The most common form factors are Extended ATX, ATX, Micro-ATX, and Mini-ITX. The Extended ATX is the largest (12 by 13 inches or 12 by 10.1 inches) and can often have eight RAM slots (for up to 128GB of RAM). The ATX is only slightly smaller (12 by 9.6 inches) but usually tops out at four RAM slots. The Micro-ATX (9.6 by 9.6 inches) can also have up to four RAM slots, but the Mini-ITX (6.7 by 6.7 inches) only has two.
Pro-tip: Every component needs to plug into the motherboard, so pick a motherboard that's large enough to fit current and future hardware.
Random Access Memory (RAM) is your PC's short-term memory — it's faster and easier to access than your PC's long-term memory (storage, e.g. hard drives), but it's also temporary. This is where the PC stores data that it is actively using (those "instruction lists" that the CPU needs to read and execute). Figuring out how much RAM you need can be tricky, because having more RAM than you use will do nothing (except waste money), and having too little RAM will negatively affect performance. Ideally, you want the perfect amount of RAM for you/your build. (But generally speaking, the average gaming rig needs 8 - 16GB of RAM.)
The most important thing to keep in mind when shopping for RAM is what your motherboard and processor can support. RAM that's faster than what your system supports will downclock to run at your system's capabilities.
Pro-tip: If you decide to go with high-speed RAM, look for RAM with Intel® Extreme Memory Profile (Intel® XMP) support. High-speed RAM will run at a standard (lower-than-advertised) speed unless it's overclocked, and Intel® Extreme Memory Profile (Intel® XMP) makes this easy to do with predefined and tested profiles.
Graphics Processing Unit (GPU)
There are two types of graphics processors: Integrated and discrete. Integrated graphics processors are integrated with the CPU. Integrated graphics have improved significantly throughout the years, though they are still generally less powerful than discrete graphics.
Discrete graphics cards are large, powerful components that plug into the motherboard via PCIe*, and come with their own resources, including video memory and (usually) an active cooling system. A discrete graphics card is a must-have for gamers who play any of today's demanding, graphics-heavy games. Serious gamers will want to look for graphics cards that produce consistent frame rates of at least 60 frames per second (FPS) at your desired resolution (anything lower may look choppy), while gamers looking to play in virtual reality should look for cards that produce consistent frame rates of at least 90 fps.
Pro-tip: The GPU isn't the only component that affects framerate, so it's important to balance out your build or you'll run into performance bottlenecks elsewhere.
Pro-tip: High-end graphics cards are expensive. If you need to cut costs, look to the last generation — the previous generation's GPU may offer similar results at a lower price point.
Storage: Solid-State Drives (SSDs, Including Intel® Optane™ Memory), Hard Disk Drives (HDDs)
There are two main types of storage: Solid-state drives (SSDs) and hard disk drives (HDDs). There are pros and cons to both, and the good news is that you don't have to choose just one.
SSDs use NAND-based flash memory — similar to, but faster and more reliable than the flash memory used in a USB stick — to store data, while HDDs store data on a spinning platter. SSDs use an integrated processor to access their stored data, while HDDs use a mechanical arm — because SSDs don't need to rely on a mechanical arm, they're much faster than HDDs (and because they don't contain a physical spinning platter, they're also generally much smaller and less susceptible to mechanical failure). The speed and convenience of SSDs come at a cost, and SSDs are more expensive per gigabyte than HDDs.
Modern SSDs come in two protocols, SATA (the older protocol, which has higher latency and lower peak bandwidth) and Non-Volatile Memory Express* (NVMe*), which utilizes the PCI Express* interface to achieve higher performance.
HDDs come in two form factors, 2.5 inches (more common in laptops, and usually slightly slower at 5400 RPM) and 3.5 inches (more common in desktops, and usually 7200+ RPM).
In addition to traditional SSDs and HDDs, there's also an option that helps bridge the speed gap: Intel® Optane™ memory storage acceleration. Intel® Optane™ memory uses 3D Xpoint memory technology to accelerate slower drives (primarily HDDs) by storing frequently-used data and access patterns. Intel® Optane™ memory learns which games you use most often and uses that data to boost game launch and level load times.
Pro-tip: You don't have to pick one. Many people use a small SSD as a boot drive (for the operating system, games, and other programs) and fill the rest of their bays with cheap HDDs for maximum storage capacity.
Power Supply Unit (PSU)
The Power Supply Unit (PSU) isn't a particularly exciting component, but it's critical nonetheless. Don't cheap out here — the PSU needs to be well-made and powerful enough to handle all current and future components, and it doesn't hurt to have a good warranty. Remember, the PSU will be powering all of your other components.
PSUs come in non-modular, semi-modular, and full-modular styles. Non-modular PSUs have all cables permanently attached — this is the cheapest option, but you'll need to find a place to stuff all the cables you're definitely not going to use. Too many unused cables result in poor cable management, which can obstruct airflow and end up affecting your PC's performance.
Semi-modular PSUs are the best option for most people — these units come with a handful of essential cables attached and are cheaper than full-modular styles. Full-modular PSUs are even easier to work with than semi-modular PSUs, but you'll be paying for the added convenience.
Pro-tip: If you buy a PSU online, make sure you buy the correct one for your country/region.
System Cooling - CPU Cooling and Chassis Airflow
PCs generate heat, and high-end gaming PCs generate a lot of heat. You will get some default cooling features with your components: GPUs and PSUs have dedicated fans and cases often come with a couple of fans. For non-gaming builds, this bare-minimum of cooling can be okay — but gaming systems usually need extra attention.
There are two main ways to cool your PC: Air and liquid.
Air cooling uses fans to funnel hot air through your system and away from components to prevent overheating. The main benefits of air cooling are cost and ease-of-installation (fans are smaller and easier to fit inside a crowded chassis). The biggest drawback to air cooling is its limitations: Air cooling depends on efficient air flow inside the case to move hot air away from components, so any air flow restriction can be problematic.
Liquid cooling uses a liquid coolant (such as distilled water) to soak up heat from components and move it to an area that's less restricted (where the radiator is placed). Liquid cooling is less dependent on air flow inside the chassis, and therefore more efficient at cooling specific components. The downside to liquid cooling is that liquid cooling systems are contained, which means they're usually larger and more difficult to install than a typical air-cooled setup (they're also more expensive).
In addition to general system cooling, you'll also need to purchase a dedicated CPU cooler. CPU coolers come in both air and liquid form factors and mount directly onto your CPU. When shopping for a CPU cooler, it's important to make sure it's compatible with your CPU and sized to fit your build.
Pro-tip: In an air-cooled system, more fans does not necessarily mean better cooling. Fan quality and placement make a difference.
Monitors, keyboards, mice, headphones, and other peripherals mostly come down to personal preference. You don't need to purchase these items with your components, but you will need a display, a keyboard, and a mouse to set up your system after you build it.
Pro-tip: Keep build balance in mind when picking peripherals — if you've got the best components in the world but you're still using a 1080p, 60Hz monitor, you won't be taking full advantage of your hardware.
STEP 1: INSTALL CPU
Parts/tools: Motherboard, CPU
Take the motherboard out of its antistatic packaging and put it on your work surface. Find the CPU socket, which will be covered with a protective plastic cap. In one corner of the plastic cap, or more commonly, on the socket itself, you'll see a small arrow — take note of where this arrow is.
Next to the CPU socket, you'll see a small metal lever. Press down on the lever and pull it gently to the side (away from the socket) to open the socket tray.
Open the CPU and remove it from its packaging. Be very careful when handling the CPU — both the CPU and the CPU socket are extremely susceptible to physical damage. Hold the CPU on the edges — never touch the pins on the bottom of the chip, because your fingers can add dust or oil, and try not to touch the top of the chip either.
In one corner of the CPU, you'll see an arrow. Line this arrow up with the arrow on the socket, and gently place the CPU onto the socket. Once the CPU has been gently seated, you can lower the retention lever down and push it back into place. Lowering the lever may require some force, but seating the CPU will not!
Pro-tip: You do not need to remove the plastic cap — when you install the CPU, the tension of the installation will cause the cap to pop off. If you try to remove the cap yourself, you could end up hitting and damaging the fragile pins underneath.
Pro-tip: The CPU only fits one way, and does not require any force to be seated. You can gently move the CPU to seat it, but do not jostle, push, snap, or otherwise try to force the CPU into the socket.
STEP 2: (OPTIONAL) INSTALL M.2 SSDs
Parts/tools: Motherboard, M.2 SSD, Phillips #0 screwdriver, motherboard user manual
If you want to install an M.2 SSD, now is a good time to do so. First, find the M.2 slot on your motherboard. It's a small, horizontal slot with a tiny screw across from it. If you can't find it, if you find multiple M.2 slots, or if you are planning on installing more than one M.2 SSD, consult the user manual that came with your motherboard.
Remove the tiny screw with a Phillips #0 screwdriver. Don't lose it.
Slide the M.2 SSD gently into the slot. When it's fully seated, it will stand off the motherboard about a 35-degree angle. Push the SSD down and replace the tiny screw to lock it in place.
Pro-tip: Installing a M.2 SSD may limit other storage configurations (especially SATA-based and PCIe* AIC storage), so consult your motherboard's user manual while planning storage.
Troubleshooting: If your motherboard doesn't recognize this newly-installed M.2 SSD as storage, you may need to manually configure it in BIOS (consult your motherboard's user manual for BIOS instructions).
STEP 3: INSTALL CPU COOLING
Parts/tools: Motherboard with installed CPU, CPU cooler, thermal paste, CPU cooler manual
There are different types of CPU coolers. For exact installation instructions, we recommend you consult the manual that came with your CPU cooler.
Some coolers require a mounting bracket. The motherboard may have a bracket pre-installed; you may need to remove this bracket if your cooler doesn't need a bracket, or replace this bracket if your cooler uses a different bracket. Do this before putting the motherboard inside the case.
Some coolers come with thermal paste pre-applied to the conductive material (which sits on the CPU) and some coolers do not. If your cooler does not have pre-applied thermal paste, you will need to manually apply thermal paste before you seat the cooler. To apply thermal paste, squeeze a small dot (no larger than a grain of rice) onto the middle of the CPU. Then, place the cooler on the CPU — the pressure will spread the thermal paste adequately.
Pro-tip: The first squeeze of thermal paste should be onto a piece of scrap paper, just in case a big glob accidentally comes out.
Pro-tip: If your cooler has pre-applied thermal paste and you want to use a different thermal paste, you can remove the thermal paste with 90% isopropyl alcohol and a lint-free cloth — we recommend an automotive-grade paper towel.
Pro-tip: When attaching the cooler to the motherboard, tighten the screws in a cross pattern to ensure evenly-distributed pressure. If you get confused, this process will likely be described in detail in your manual.
Troubleshooting: If you mess up the installation, don't panic. Clean off the thermal paste (from both the CPU heat spreader and the cooler) and re-apply, then install again.
STEP 4: INSTALL MEMORY (RAM)
Parts/tools: Motherboard, RAM, motherboard user manual
Determine how many RAM slots your motherboard has (most have either two or four). If you're going to fill all available RAM slots, simply snap the RAM into place. If you're not going to fill all of the RAM slots, consult the user manual to find the correct configuration and populate the RAM slots accordingly.
Pro-tip: The notch between the gold fingers is not centered. Make sure you're aligning the RAM correctly using this notch to determine which side is up versus down.
Troubleshooting: While RAM is relatively easy to snap into place, it doesn't always snap in perfectly the first time. If you try to turn your PC on and it doesn't turn on, the first thing you should do is re-seat the RAM. Some motherboards have a captive tab (one you don't have to move) that helps with installation. All motherboards have at least one tab that does move — usually, it will snap into place and attach onto an indent on the side of the RAM.
STEP 5: (OPTIONAL) DO A TEST RUN OUTSIDE THE CASE
Parts/tools: Motherboard with CPU and CPU cooler installed, RAM, GPU, PSU, screwdriver, motherboard user manual, PC monitor (attached to GPU)
Now that you've installed the CPU and the CPU cooler, you may want to perform a quick test run of your components just to make sure they all work. This test is much more difficult to perform (and troubleshoot) once everything is installed in the chassis. To do this, install GPU and connect everything to the power supply (if you don't know how to install the GPU, see section below). Make sure the power supply is connected to the motherboard (both CPU 8pin and 24pin) and GPU, then plug it in and turn it on.
Some higher-end motherboards have power buttons, but many do not. If you don't see a power button, locate the power switch pins — small pairs of prongs sticking out of colorful nodules. The power switch pins may be labeled (something like "PWR_ON"). To turn the motherboard on, use a screwdriver to tap both power switch pins at once.
You should now be able to tell if any of your components are dead or otherwise malfunctioning. If your motherboard is blinking lights or beeping at you, it's probably trying to tell you something. Some motherboards have a post code display (two digits) to help you identify what the problem is. To figure out what it's trying to tell you, consult your user manual. If your motherboard has no post code display, connect a display to the GPU and see if your system "posts" or starts up and displays the motherboard's logo.
When you are finished with the test run, turn off the power supply and wait for any LEDs on the motherboard to go dark to ensure there's no residual power in the system. Then, uninstall the GPU and unplug all power cables before proceeding with the next step.
STEP 6: MOUNT POWER SUPPLY
Parts/tools: PSU, case, PSU cables, Phillips #2 screwdriver
Unpack the PSU (or unplug it from the components if you opted for a test run) and set its cables aside (if you can).
Take a look at your case and figure out where the PSU is supposed to go (probably on the bottom, near the back) and how it can be oriented. Ideally, you want to orient the PSU so that its fan faces outside the case (via a vent). If your case has a vent on the bottom, you can mount the PSU upside down, so long as the bottom vent will receive decent airflow when the PC is finished.
If your case has no vents, mount the PSU so the fan is facing up (into the case) and make sure it has enough clearance.
Attach the PSU to the case using the four screws that came with the PSU.
If you're using a non-modular or semi-modular power supply, now is the time to run the attached cables through the case to where they'll need to end up (make use of cable management features if your case has them).
STEP 7: INSTALL MOTHERBOARD
Parts/tools: Case, motherboard, I/O shield (if not attached to the motherboard), Phillips #2 screwdriver, screws, motherboard user manual
If your motherboard came with an unattached I/O shield — a rectangular sheet of metal with cutouts for the motherboard's ports — you should first snap it into place in the back of your case (make sure it's oriented correctly). I/O shields usually have sharp edges, so watch your fingers.
Once the I/O shield is in place, you can install the motherboard. Double-check to make sure your cables are all threaded through to the correct place, and then place the motherboard (align it with the I/O shield, first). Using a Phillips #2 screwdriver, mount the first screw — the center screw — to hold the motherboard in place. Make sure you do not drag your motherboard across the standoffs attached to the chassis.
The number of screws you will need to mount the motherboard will vary based on the board, but a full-size ATX motherboard usually takes 9 screws. Fill all available screw holes.
Connect the power supply to the motherboard. There are two main connections — an 8-pin CPU connector toward the top of the board and a 24-pin connector from the side.
Pro-tip: Before you mount the motherboard, check to make sure the case has motherboard standoffs installed. These usually look like a nut with threading on the end. Do not insert unnecessary standoffs.
STEP 8: INSTALL GPU
Parts/tools: Motherboard, GPU, Phillips #2 screwdriver, screws, motherboard user manual
Find the PCIe* x16 slot on your motherboard. It will be the longest PCIe* slot and may be a different color than the others. If your motherboard has more than one PCIe* x16 slot, check the user manual to see if one slot needs to be prioritized. If any slot can be used, determine which slot you'll be using based on where other components are placed — you want your GPU to have some breathing room.
Depending on your case, you may need to remove I/O covers (small metal tabs blocking the back panel of your case) to accommodate your GPU's I/O (HDMI, DisplayPort, DVI, etc.) and make it accessible to the exterior of the chassis.
Remove the GPU from its antistatic packaging and carefully align it with both the rear retention bracket and the slot itself, and then gently push it into the PCIe* x16 slot (you may hear a click). The PCIe* tab on the motherboard may move into a locked position should you need to reseat the GPU.
Once the GPU is fully seated, secure it to the back of the case using one or two screws. If your GPU requires auxiliary power connectors, connect it to the power supply.
STEP 9: INSTALL STORAGE
Parts/tools: Motherboard, SSDs, HDDs, Phillips #2 screwdriver, screws, case/chassis user manual
Look at your case — every case is a little different when it comes to drive bays. You should be able to find a stack of bays in different sizes somewhere inside your case. They may have little plastic switches, in which case they are tool-free bays, or they may just look like metal brackets. Storage generally comes in two sizes, 2.5-inch (HDDs and SSDs) and 3.5-inch (HDDs). Most 3.5-inch bays can accept 2.5-inch drives, but not vice-versa (some 3.5-inch bays will have trays that aren't designed for 2.5-inch drives, but they can still fit 2.5-inch bays). You may also see larger bays in your case — these are for larger drives such as optical drives and are usually located in the front of the case, near the top.
If you have tool-free bays, each bay will have its own plastic lever or switch. Open or unlock the lever or switch and you should be able to pull out the tray. Place your drive in the tray — some 3.5-inch trays will be designed to accept 2.5-inch trays. If they are, you'll need to screw the 2.5-inch drive to the 3.5-inch tray so it doesn't move around.
Slide the tray back into the bay. It should click into place.
If you don't have tool-free bays, you'll see a metal bracket (it will be big, like a sheet), with slats or holes in it. To put a drive in one of these "bays," all you have to do is slide the drive between the metal bracket and the side of your case and screw it into place. Use as many screws as the chassis manual recommends, but if you don't have enough screws most drives will be fine with just two screws.
Once your drives are all in place, connect them to the motherboard (using a SATA cable, which should have come with either your drive or your motherboard) and to the power supply.
Pro-tip: If you have trouble finding the bays or figuring out what type of bays your case has, consult your case's user manual.
STEP 10: INSTALL OPERATING SYSTEM
Parts/tools: PC, monitor, mouse, keyboard, OS saved to a flash drive
Now it's time to install your operating system (OS). Determine which OS you want to install on your PC and download the installer on a flash drive. You can download the installer for Windows* 10 here. If you are installing a paid OS such as Windows, you will need a product key.
Plug in the flash drive that contains your OS, as well as a monitor, mouse, and keyboard, and turn on your PC.
The first screen you see will tell you to press a key to enter the system setup or BIOS. Press the key to open BIOS. (If the screen flashes off too quickly for you to see the key, consult your motherboard's user manual.)
First, you'll want to check to makes sure your components are all installed and being recognized. Find the page in BIOS that shows your PC's system info (different motherboards have different BIOS setups, but you should be able to find a screen that gives you this information) and check to make sure the system is recognizing everything you've installed so far.
Next, poke around BIOS until you find the Boot page (may be called "Boot Order" or "Boot Priority"). Change the boot order so that your flash drive is first and the drive you want to install your OS on (if you're using an SSD as a boot drive, you will want to install the OS here) is second.
Restart your computer. Your computer will boot from the USB and the OS installer will pop up. Follow the instructions to finish the installation.
Pro-tip: Create the OS installer ahead of time.
Troubleshooting: If the PC doesn't turn on at all, you might have a problem with your power supply.
Troubleshooting: If the PC turns on but you don't see anything on the screen, or it doesn't seem to start up, check to make sure all cables, especially power cables, are connected.
Pro-tip: If you're trying to enter BIOS with your keyboard and it's not working, it's probably your keyboard that's not working. Check your peripherals to make sure they're working before you panic.
Troubleshooting: If you have trouble booting to the USB drive, ensure the motherboard is set for the installation type you are attempting. Most UEFI-enabled platforms will boot to the UEFI partition scheme first before attempting Legacy.
IT DOESN'T END HERE
The best thing about building your own gaming PC is that the job is never truly finished. You don't just have a custom-built gaming rig, you have a work-in-progress that will always be as current and as cutting-edge as you want (or, as you can afford) it to be. Now, when the next demanding game comes out, you can just swap out your components instead of suffering through choppy details and poorly-rendered landscapes.