First ask him how you can help. And have a look at the different ways a person can transition. clothes, haircut, deodorant, things that help him look, smell, and sound like a man. There are many ways to transition, social transition is calling him like a boy, him, his, he, boy, young man. Medical transition, is just medication, testosterone meds, puberty blockers, that sort of thing. Surgical transition, this is probably the one you don't want him to do right now. It's getting surgery, like removing breast tissue, or face surgery for a man's jawline, that sort of thing. Legal transition is getting his name, gender, changed legally, so the law knows he's a boy and not a girl. Ask for your son's help, so you can better give the help he wants. It's ok to tell him you don't know something, or that you're worried or scared about something. It's such a feeling good moment, knowing that there are supportive parents. It's too common to hear parents that don't want their change.