How do I removed flab from my thighs?

Sorry, there's no partial reduction on flab. We are all genetically pre-programmed where our fat will be stored in our bodies. But not to worry, being a male, you have far less chance to have oversized thighs. Chances are you'll out grow it, then the belly flab will kick in when we (men) age :( oh, well....guess we can't win it all.

Excercise. Workout, do cardio and eat healthy foods. There is no magic solution. Just hard work, dedication and will power.

Your "problem" is simple: genetics....
you were born this way and the size of your thighs (as well as the "skinniness" of your upper body) is part of your body-shape "program".

Exercises that concentrate on working on the muscles of your lower half might help in tightening up and thereby reducing the size of your thighs but, yours will be a life long battle. More aggressive action, such as Liposuction, would remove some of the genetically produced fat but face it, some of us are tall, some of us are short, some are skinny and some are overweight....not because of any action on our part but simply because that's the way we were genetically engineered to become.

The good news is you're only 15 and your body hasn't completed it's growth yet. You don't know at this point just how you'll end up...you could still grow taller by a couple of inches or more and, your legs could develop without the large thighs. I wouldn't worry about it and just continue to exercise and eat healthy and "let the chips fall where they may".

Have you tried running? That will build some muscle, and convert the fat into muscle!

workout regularly doing toning exercises which will help burn the fat and what you don't want to hear just wait it out since your still growing, some of that is probably baby fat since you still have a lot of growing to do. you'll probably be growing on average until your 21 or so.