How to do the splits?

Hi, im 11 years old ( on my aunts acc who let me have it ) and im gonna start ballet soon.....my aunt told me i have to do lots of excercise so i can get fit and do ballet very well....im about 120 lbs and im 5.1 or 5.0......im asking if my weight is ok for ballet....and how to do the splits?? also will i break my legs if i just streatch it all the way or my aunt puts each leg on the side? Thank you :)