How do i get Fatter legs?!?!?

I am a 12 year old girl turninqq 13 in July n on my birthsay its summer n i want to wear dreses but i cant cus i am ashamed of my little chicken leqs! I wight like 95lbs.(Yupp im skinny as hell!) But my parents say its okay cus im really pretty but idk anyways...Somee ppl Say qo swimminqq or Wait untill im 17. But heres the problem w/ that I dont kno how too swimn i am IMPATIENT! So yeah wht shouldd i do PLEASE help me!