How can i slim down my legs fast!?

Ok im 15 in june and i am 5'1 and 100 pounds. Yeh thats light and skinny but i have thunder thighs and huge calves. I wanna them to get smaller idx care if i loose pounds but i really want them to look small... I tried in a mini dress and i didnt buy it cuz my legs were ugh! Lol and another thing and i cant resist junk food were a fanily of 8 so were gonna have junk food could u guys give me like a varaity of healthy foods and how to keep my self from junk please and exercise that make my legs look smaller and not muscular thanx =)