If you are a seasonal guest, then you will receive an e-mail from RCN inviting you to come and pick up your free Thetford card at the reception desk.
If you enjoyed your experience trying the Thetford machine and would like to reuse it in the future, you can do so by registering the free Thetford card that you received. Simply click on Sign in and follow the instructions to register your card and buy some credits. These credits can be used on any Thetford machine.