You can participate in a tournament by ‘buying in’. If it is possible to make a "rebuy" or "add-on" bet, you can select them on the tournament page of the tournament you are participating in. A "rebuy" allows you to re-enroll in a tournament with a new score. You can do this as long as there are rebuys available. An "Add-on" means that you can buy extra playing time and/or credit. Extra playing time can be interesting when you don't have enough time to use your credit. Extra credit can be interesting when you just have some time left and you want to gain some additional spots in the ranking.