There are in fact special exercises for belly fat because each exercise stresses certain muscles in your body, so riding a bike for example will be more exercise to your leg than to your shoulders.
Some of exercises to lose belly fat that do not require equipments are:
Bicycle Exercise: Lay down on the floor on a supine position putting your hand behind your head and start as if you are paddling a bike but with your elbows.
Interval Workout: The basic idea here is if you exposed your body to intense exercise (or resistance) then give it less intense exercise then intense again, you work out your abdominal muscles and therefore reducing belly fat. This could be sprinting for 5 minutes then walking for 10 minutes and so on.
You combine all these exercises with low fat diet or more accurately focus on unsaturated fats rather than saturated ones. Unsaturated fats you get from olive oil which kills the bad fats you get from cooking oil). Knowing how to gain weight will help you avoid the foods that accumulate fats around your belly or under your arms so make yourself familiar with those kinds of foods to know what you up against.
Learn so you have better knowledge of foods that are rich in calories. This way you can build your weight loss diet yourself.