You use the card, near the end of the month, you get a bill, and you either write a check to pay off that bill or do what I do, since I have Citibank Visa and Mastercard's, I go to the bank itself and pay them off (they give you a certain amount of time to pay the monthly bill). Get a card that doesn't charge you an annual fee, not sure which actually do anymore. By the way, you don't have to pay off everything, you just have to pay the minimum they have stated, but anything that you don't pay off gets charged interest...
edit: Yeah, you write a check and send it to them through the mail.