I was wondering if anyone could suggest a way to gain courage, to tell my parents about me being depressed?

Just do it. Sorry that seems vague but that's what you got to do when it comes to anything you're dreading, is just do it. You'll feel better once you do.

The best way to confront a fear like that is to go out and do it. The more you think about it, the more you're going to overthink it and get bogged down in the possibilities. And if it's something you're worried about, you're only going to see the negative possibilities, and that's going to make it even harder.

If you can't do that, just write out what you want to say. Practice it a few times to yourself, in front of a mirror. Then go out and do it. Just write the opening part... you don't want to think too deeply into the conversation, as that will lead you into the trap of feeling out of place if it goes in a different direction than you expect it to.

If you can't tell your parents, why don't you go see a professional by yourself? Maybe a psychologist... Is there one in your school?

I don't know how old you are, but it might be a good idea.

I agree as well as difficult as it may seem it's easier to just take a deep breath and spit it out. You will probably feel some relief knowing it's all out in the open