Do you know what colors are, how to read basic letters such as A and B, and basic shapes such as squares?
If you answered yes to that question then you can build a computer. Never buy pre-built.
Pick a pretty case
Pick a CPU
Pick a Motherboard with socket that matches CPU
Pick on 2 RAM sticks
Pick out power supply to power your parts
Pick out GPU to run game, google benchmarks to find what you want
Pick HDD with enough space
When everything arrives match the colors together, put numbers and letter together, and put shapes into shapes.