A lot of people worry about their tummy. It's a difficult one! Exercise alone won't do much good. If you want to lose weight, you'll need to diet as well. Veg, fruit, protein,... Remember, as a woman, you need a minimum of 1200 calories a day.
Now, there's plenty people on here who can give you much better advice. But in ways of exercise, go for cardio and abs workouts. The more you sweat, the better. Just make sure you stay hydrated with plenty of water.
Besides the ab workouts, Janna has it right. You can't target fat loss, you can only target where you gain muscle mass, so if you do ab workouts, your tummy will just look bigger, because you gain muscle mass under the fat.
I know people say 1200 calories... But rather than counting calories in everything that you eat make sure you good healthy food. Low fat, low carb, high protein diet. I'm currently doing work placement in Nutrition and that is what I find most dietitians tell their clients. Because when you start counting calories you can easily get discouraged and starve yourself if you go above the recommended amount.
Exercise is also very important. Cardio is probably one of the best forms. Do HIIT workouts for atleast 20 - 30 mins a day