Coming Out?

Three people know I’m bi, my mom, one of my best friends, and my ex best friend. But I live in a very unaccepting/conservative school district (I’m in high school currently). I want to come out but I don’t know how to without losing friends and I’ve never done anything with a girl and I don’t want people to invalidate my being bi because I haven’t done anything with a girl. Any tips or words of advice?