Re: Can't build computer properly
Probably but I'm not sure. I know it's no help saying this now but that's why you should always do a bit of research First. And what I'll say next probably won't be much help either seeing as you've already bought your components.
Don't worry yourself about Thermal paste, The pre-applied Paste is sufficient in all ways. For Cases, apart From the obvious reasons it's depending on what you want From your Case. I'd say swap your Case if you're having troubles. Either way your best bet is to go with a Case From The Corsair Carbide range. Specifically For mid-budget projects a 200r/300r Case is ideal. Cheap, good and reliable. But apart From that I can't make sense of why you went with that Motherboard. You've got a really crappy PSU but a pretty decent Mobo. Stick with Z77, But Extreme 4 is probably a better Mobo than what you need.
Again your best bet would to be to replace that PSU immediately. As I learned From PP Mguire one thing you definitely DON'T wan't is a bad PSU. 600W is Fine, it's just the "CX" = Builder Series. "TX" is what you want, which is Enthusiast. Even though you may not be an Enthusiastic computer user or whatever, it's a PSU you ideally should want.
But there's plenty of 'How To' videos on YouTube and the Internet. Newegg have an 'okay' guide, but visit the YouTube channel "LinusTechTips" or "NCIXcom" / "NCIXTechTips" or "TimeToLiveCustoms" They give daily advice and cover nearly every part you could ever want to use, and I'm pretty sure both of them have How To Build a PC videos.