Losing belly fat primarily comes from diet, however you can raise your metabolism to burn off more calories per day by doing strength training, circuit based training (HiiT with free weights or bodyweight) or HiiT Sprints outside or any cardio machine. For even quicker and more prominent results, try combining a mixture of strength training and HiiT.
Strength training will allow you to build lean muscle, which will actually boost your metabolism too. Don't be discouraged thinking weights will bulk you up (this only happens when you eat more calories than you burn off), you'll physically change the shape of your body with strength training, while burning off excess fat from the cardio and weights combined.
Remember, while ab workouts are awesome for strengthening your core and building your stomach muscles, you CAN'T spot reduce fat by training that particular area. Get a good full balanced training plan in place, dial in your diet to reduce fat and stay consistent...we promise you'll see much better results.