When should we prepare for Yale or other Colleges?

I’m just 15 years old and I really want to apply to Yale, but I’m living in Germany, in a small town so it’s really hard to find someone who’s in Yale ever before. Have you been accepted at Yale even when you are not the “super geek” or the natural “businessman”?
I’m a asian girl, ambitious, diligent and a little bit too quiet …
I have the feeling that I am really average.
I really want to apply to Yale, since I was 13-14 years old. Hope you all understand my feelings …
Thanks for your attention :).
-Collegina