When/if you get the parts you'll find it remarkably easier than you might think.
It's almost impossible to get it wrong (Unless you drop a beer on it or something.)
CPU, RAM and Graphics card sit directly in the motherboard. Optical Drives and Hard Drives plug in to the motherboard through obvious cables. The motherboard requires two obvious cables to power it, the Optical/Hard Drives also, then plug your fans into the motherboard.
It's really quite simple. You seem to think you're going to be manually wiring each part.