The basic of building a computer is to put/connect parts together. It's very seldom that you have to screw things tighten, but it happens.
The first thing that happens is that the mainboard/motherboard comes out of the package and is unwrapped.
Then the fun begins.
This is the Asus P5E X38, 775, DDR2
RED: CPU socket
YELLOW: RAM slots
GREEN: PCI Ex16 slots
PURPLE: PCI slots