The quickest way to reset your poker account password is by clicking Forgot Password at the poker log in screen. If you have set your account to log in automatically you will need to disable this first.
To disable auto login click Settings -> System and untick Auto Login.
Once this is done, to reset your password just restart the poker software and click Forgot Password. You can then follow the onscreen instructions to either answer a secret question and change your password, or if you prefer you can choose to have a new password automatically emailed to you.