The belt pulley to the left of the crank. I took off the pulley, then I took out the allen screw under it. It popped out and there was this big spring. Now I can't get it back on the right way. What did I do, and how do I fix it??

 

I mean, I can get it in, it's just off... Like the threads for the pulley are too far down.

 

Why did you remove it like that, you know that it's supposed to come out by removing the 2 M8 bolts that holds it to the accesory bracket. Remove those bolts with a 10mm wrench or socket and try to fix every thing back in the housing outside the car. That spring should be under good preload. Consider that this piece is around $30 so you might not want to waste more time or injuring yourself strugling with it.
Good luck