There are 2 ways to log into Blackjack: as a Guest or using Facebook.
When you first start Blackjack, you are automatically logged in a guest. You can continue to play as a guest or you can login using a Facebook login. You can add a Facebook Login by going to the Account Information screen found within Blackjack under Settings. Settings can be found by tapping the Gear icon on the top right of the Blackjack table.
If you have logged out of Blackjack and are presented with the Log In screen, you have 2 choices: Facebook or Play As Guest. If the guest selection is not available, you have already added a Facebook account.
If you are having trouble with your Facebook password, you will need to open Facebook on your browser and follow the forgot password directions.
Once logged in you can see your account information by looking under Settings and then selecting Account Information.