When you first enter a tournament you'll be automatically placed into a qualification league.
Every player in your league will then play up to 9 matches. The lower your score the higher up the leaderboard you will finish!
In order to qualify for the next stage of the tournament you will need to finish within the top 50% of players in your qualification league.
Don't worry if you fail to qualify as there are a total of 3 tournament qualification sessions. Each session lasts for 1 day and they run on Monday, Tuesday and Wednesday.