Welcome to JustAnswer.
You can either write them a letter or email, you can have someone else tell them, you can call them, or you can sit down with them in person.
Some people write letters, send them, have their parents read them, and then (a few days later) sit down and talk about it. That way, you can tell them in writing where they don't interupt or stop you to ask questions, and you get to say what you want them to know. Then, you can sit down, reexplain, and they can ask questions. After they read your letter, they will have a few days to let it all soak in.
I hope this helps!