hello i am bkue belt and I would like to participate in the championship
You just have to play ranked games to be in, no need to sign up.
There should be a "Matchmaking" button on the lower left corner when you're playing Toribash. Use this and be sure to play ranked games, not unranked ones.
You can check your current rank here.
Ranking is so unbalanced, since everyone starts out with the same ELO at the beginning it's very difficult to climb at first, so anything you do in the beginning is basically useless, if you start matchmaking during the last 2 weeks or so everyone has a high ELO and it's basically the only time you can climb properly, so there's no point in even playing matchmaking until the last 2 weeks.