Part 1. Buy the right bits, posting a spec in General Hardware will help you avoid and snaffu's here.
Part 2. Put it together, I suggest doing it outside the case in a trial run - it's not necessary but it's easier to see if cards, memory etc. are properly in. People can forget that for the first time builder not knowing how hard to push something can be a problem, being able to easily see if it's gone all the way in is a god send.
I'm sure there are youtube videos too - plus the help of General Hardware if you're unsure of anything.