This changes from tournament to tournament depending on the style of tournament. But in all tournaments you play each person twice, once for each colour. In all tournaments, it is 3 points for a win and 1 point for a draw.
Right now there is a grand tournament open and a Duel tournament. They work slightly differently. In the Grand tournament everyone plays everyone, and the winner is the peron with the most points. In the Duel tournament, two players play each other and the overall winner advances to the next round, this happens till the last group of players play each other. At that point the winner of the last group is the winner of the tournament.