Good luck with telling your parents. Also FtM from Australia here. I'm 17 and I came out to my parents around last September and will be going on T in April already. Would've actually been sooner but I have to be 18. If you live in Sydney I can help you out with where to go.

You can just tell your parents you're questioning your gender and ask to go to a gender therapist (even though you're fairly certain you're male) then have the therapist confirm it to your parents. Or just tell them straight up that you don't feel like a girl, and you feel male. You don't really have to say the exact term 'transgender' to them, I didn't. I just told my parents I don't feel like a girl and I never have. They were really confused at first as they weren't educated on the topic and they thought my therapy was going to convince me I am a girl. But, after they educated themselves they were very accepting.