Please go to the check-in counter as you usually would to check in for the flight with the credit card holder and the necessary documentation. The check-in agent will be able to verify the payment card there and issue you with your boarding pass. Note that you will not be able to download a mobile boarding pass if you have to verify your credit card at the check in desk.
Please make sure that you allow extra time at the airport for the credit card verification process. If you miss your flight, cancellation penalties may apply in accordance with the terms and conditions of your ticket.