I would not tell chess.com my age, especially if you are a minor. That is dangerous and no one needs to know that information. Instead, tell them your rating.
As for advice, I suggest you get a good night's sleep, do some puzzles to warm yourself up, go over your opening preparation, and take your time. I haven't competed in a tournament myself but I have heard about it somewhere. I'm sure you can find a book about what to do to prepare for a tournament.
I am a 730 and I am preparing for a 25+5 increment Washington state tournament. How do I prepare? Note: I have a diamond membership