The easiest way is to go to the Guest Relations Desk and give them the money you would use for gambling to be applied to your account. (Not sure they will take a payment higher than your current balance though.) Then when you go to the casino you insert your card in to a machine and create your "players bank" you transfer the same amount of money into your bank. Say its $100. A $100 charge will appear on your sign and sail account. The charge for the money and the deposit will offset each other. Or you could just make the transfer and then pay the money to your account later. The final sign and sail balance does not get charged to your credit card until the end of the cruise, so as long as you pay your "gambling balance" before the last night you won't see it on your S&S account charge.
I THINK you can also just go to the casino cage and hand them money which can be deposited onto your players bank too but I have never done this. IF you are playing table games though none of this matters since the "points" are tracked by the pit bosses on the floor anyway. You need to give them your sign and sail card and tell them you wished to be tracked for points in the players club on the FIRST night of the cruise so they can monitor and add points to your account while you are playing the table games. Otherwise you won't get credit. The only time you will start earning points else-wise is if you win about $400 or more (not sure what the actual number is but is seems to be about this) Win that much and the pit boss will ask to see your S&S card during your cash out... after which time you start to be monitored and tracked. The tables all accept cash buy ins.
Hope that helps.
Just remember that if you do use your sign and sail card that you cash out THE LAST NIGHT at the casino cage. The player bank money and the sail and sign account are two different accounts. If you don't pull any left over balance OFF the bank on the last night you are going to lose it as the Casino cage is close the next morning when in port for disembarkation.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14, Freedom x 2 6/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013