How do I lose belly fat?

I got on the DEPO shot and gained a TON of weight but all in my belly. It looks like I have a tire around my stomach. Its nasty. I also have lost all of my a**. It went soooo flat! I used to have a perfect coke bottle shape. Well now im off the depo for GOOD! And getting on another type of birth control.

Anyways how can I lose belly fat? Like what exercises will help that section the most?