What can I do to flatten my tummy?

I am a teenager 18 years old, I have a good figure my legs are toned my butt is tight my arms are in good shape the only problem is that I have a little tummy that I can't seem to take it out. I eat good healthy, vegetables fruits don't eat too much junk food but I don't know what to do to get the fat out of my tummy! PLEASE SOMEONE HELP. It's the only thing I need in order to look good in a bikini :)