everytime i start to download it, it says error code 1390 or something like that
i don't know how to fix it and it's really pissing me off
HELP ME!

Okay. Itunes is having some problems right now.
It's happening to everyone. The problem lies with apple, not you.
It's the 11th, and everyone was frantic to get a $200 iPhone. Apple didnt predict the traffic correctly, so their servers have all crashed.
It'll come back later. Just give the techies some time to fix it.