From in the CasinoUnreal Software select the Poker Tables tab and simply double click on the tournament you would like to enter.
If you are eligible to enter the tournament the 'Register' button in the bottom right hand corner will be clickable, just click on this button.
You will then have the Registration confirmation window pop up.
Your name will appear shortly in the player list. If you need to de-register from the tournament simply click on the Deregister button beside the Register button.
You will then have the De-Registration window pop up.