Actually if you were less of an arrogant child my comment would reveal that
A - You cannot manage a simple task of lining up the PSU so you need to gain help from somebody less hand eye co-ordination challenged than yourself
B - The case is damaged in some way
C - You need to learn how to describe a problem rather than demanding help with a vague issue and a large over inflated and unearned sense of personal worth.
Also do you realise how utterly stupid your question is. The answer to your question is "you are doing it wrong" where you to be able to galvinise a brain cell enough to actually describe your problem maybe people could help you further..... ie WHY wont it fit whats actually going wrong?