To add a payment method:
Login and navigate to the icon to the right to select "My Account." On the 'My Account' tab, look for "My Payment Method," and click the link 'Add one now.' All set!
To update a payment method:
Navigate to the icon to the right to select "My Account." On the 'My Account' tab, look for "My Payment Method," you'll see 3 dots next to your existing credit card info. Please click 'Update settings' to save the new payment method!