How do I get into N.A.S.A. of a enginer? Is it hard?

Hi! I'm am 14 years old and I work very hard in school to become an Aerospace engineer. I would really like to work for N.A.S.A.. All my life a have dream of space and exploring it. Please, oh please, give me some advice. I would like to know, what coarses do I have to take and also give me some steps. To make this simplier, what do I have to do to make sure i'm accpected in. How can I make my self look good because i'm completely lost. All I know is get good grades and go to a good college.