There are two ways to save a payment method to your Adafruit account. You can save a payment during the checkout process or by updating your Payment Methods in your Account Settings.

How to save a payment method to your account during checkout. 

Log in to your Adafruit account. Next, add all the items you need to your cart and then visit checkout. At the payment step, you will see Credit Card (Stripe) as an option. Select that.

Enter your credit card details. Make sure to check the box Save this payment method for future orders. Finish checkout and you will see the success page.

Next, visit My Account Settings > Payment Methods to confirm you are seeing the payment method you just saved.

From this page you can make this payment method the Default, Edit the address associated with the payment method, or Delete this saved payment method

On the Payment Methods page in your Account Settings, you can also save a new Payment Method. 

Select the Enter New Credit Card button. On the next page, enter the billing address by either selecting an existing saved address or scrolling to the bottom of the dropdown menu and selecting New Address.

On the following page, enter card details. Please make sure your card details are valid or you will see the following error:

After you've entered your valid CC details, select Save New Card. Next, visit My Account Settings > Payment Methods to confirm you are seeing the payment method you just saved.