Enter in your Gift Code when you sign up . See below for the exact spot. Gift Codes are case & space sensitive so be sure to use all caps & no spaces if the Gift Code comes that way.
When using a Gift Code you must enter in a credit card, however, your card will not be charged until the Gift Code expires.
If you do nothing then your card on file will be used to start the membership subscription that you selected.
Cancel your subscription before the Gift Code expires and your card will not be charged. However your membership can be reactivated at any time in the future by logging in and selecting the “update payment info” button at top then the “update” button next to your subscription.