Diet and exercise plan for flat stomach? .?

Im seventeen, 5’4”, small frame and 116 pounds. The only problem is my stomach, which I would really love to be flat, especially since its getting to be swim season.

What exercise can I do to get a flat somach?

Also, how do i lose that fat off the somach? (because when i just do situps my muscle builds up but the fat stays on top).

What should I be eatting for my main meals, breakfast, lunch and dinner.

p.s. it would be great if this flat somach happened in a month or so.