If you’re not sure about your friend’s orientation, it can be helpful to have general discussions with them about sexuality and desire as a starting point. This way, they will become aware that you are interested in same-sex relationships, and hopefully you can get a better sense of their own interest. If, after such conversations, you still don’t have an idea of your friend’s orientation, be honest and open up about your interest, trusting that the strength of your friendship will help you work through any difficulties that may arise. Privacy is also important. Telling a friend in front of a bunch of other people isn’t clever. Find somewhere private, just you two.
If your friend doesn’t want to talk, don’t force them. Accept their feelings and move on, whether you want to stop being friends or stay friends.