I'm 15, I weigh 170 lbs and I'm 6'2"
When I was about 10-11 I was quite chubby but then I found an interest in sport and turned a lot of the fat into muscle.(I also got a lot taller too) Playing high energy sports like tennis helps a lot. I still have a really bad habit of eating late at night which can cause weight gain, it's a good thing I exercise.
Just find a sport you enjoy and commit to it, no matter how bad you are, you'll get better. And eat good proportions, your meal should consist of palm sized sections, so a palm sized piece of meat with a palm sized about of rice/pasta/potatoes and a little more than a palm sized amount of vegetables, but remember fat is needed, so don't cut down on every single thing that is fatty, cut down on saturated fats, they're the bad ones