In order to reconcile a credit card, the credit card must be set up like a bank account so that you can create reconciliations for that account. For more information on setting up accounts, click here.
After you have set up the credit card as a bank account and have began to accrue activity, you will start a bank reconciliation for that account. For more information on bank reconciliations, click here.
The main thing to remember when starting a bank reconciliation for a credit card account, is that the credit card is a liability. Consequently, you will need to change the beginning and ending statement balances to be negative. Then check off your transactions as you normally would to reach a difference of '0' on the bank rec.