Before using your tickets, you should check which ones you have. To do so open the PokerStars client and log in. Then click 'Tools (1) > My Games & Tickets (2) > Tournament Tickets' to see a list of the tickets you have currently in your account.
How to use your tickets
To see a list of tournaments that you can use your ticket for simply select that ticket (3) and you will then see below a list of available tournaments. To find out more about a tournament just double-click on it (4) and the tournament lobby will pop-up on your desktop.