What type of tournaments? For daily tournaments just play during the scheduled time on the proper game rooms. For player-organized tournaments check the boards for active tournaments and check if you can join.
Depends on the tournament rules. Most of the time players are put into groups the thing is you must play everyone in your group at the danger zone. This matches depends on when you and your opponent might be available.
If you accept in mostly there are groups watch there make the fights with the oponents in your group and then you have wait after the first phase maby you go to next round ore you are out