@craigt - Go to the payment TAB on the left of My Account...go to Manage Payment Method...then Update Card Information.
If you are having site issues, try clearing your browser's cache, or try a different browser or device.
But best and easiest way, I find, is opening a tab in incognito mode then log in this way.
If you have not created/registered for a My Account yet, you can submit a ticket here to: Create or forgot My Account email or password link
