How could a 13 year old tone up before summer?

I'm 5'1 and 121 freaking pounds, with a lot of leg muscle. I also have big bones (not an excuse, my ribs and hip bones poke out). And I may feel fat, but I know I'm not. I'm definitely not. I seem to gain a ton of weight and then get way taller, but I want to tone up my muscle and burn some fat before summer. Actually, I don't care if it's before summer, I would just prefer it. I have a bit of belly fat and thigh fat. Are there any exercises that would tone up my stomach and thighs (Like, all of my thigh muscles) while burning fat? But I don't want big bronco thighs.