If you have a little round belly like me, do a lot of running
Since you are still young, I don't recommend working out yet
Maybe you can start in the summer, just do a little training with supervision
As for your diet, just have healthy balanced diets, but once you start exercising, then increase proteins' portions
So have more meat, eggs, etc ..
You can also do crunches, preferably like the ones in the picture below
Hope this helps you out