How do i get my straight female friend to have sex with me?

i have this friend who i guess i like and i think of her sexually alot. i have always only been with guys but i don't know i think i like her and i really want to have sex with her. we have been good friends for a while. i don't think she likes girls but my bestfriend says she acts like it at times. what should i do? how can i know if there could be a possibility she likes girls?