How do you ask one of your crushes to the winter formal?

Well its this new boi at my skool and I want to go to the winter formal but I don't know how and when to ask. See he is new but i like him I think he likes me back and I am tring to avoid my feelings getting hurt if he rejects me. Then on top of that my ex boyfriend wants to go with me and has planned to ask me at the movies on Saturday of 11-25. help me please.