Serious question please ! i dont know how to masturbate im almost 17 i never have?

You're fine and its normal. As for being nervous about getting an erection: don't worry about that either. When your body is sexually stimulated, you will begin to notice a change, and it'll be painfully obvious (: don't worry about it. Try working on yourself in the shower, that's the easiest place to let the stress of it go and focus on pleasure.