How do I improve my turnout?

I was asked to join a pointe class next year. I am 13 and have been dancing for about 8 years. My teacher had me stay after technique class, sit on the floor, and point my feet as hard as I could. She said I don't have a natural turnout so if I improve my turnout by my class next week I will be able to join pointe classes next year. What exercises can I use to improve my turnout?