The older version (2.1.3) requires a card to be inserted and a pin entered for a demo game. The pin can be any number and the card just needs something encoded on it. The 2.1.3 version used a $0.00 buy in MTT profile for demo games.
The newer version (4.X) has a "Login" button on the player screens for demo games.
The game profile administrator will have a Demo option in some form in both versions.