To update your credit card for your plug&paid Supercharged plan visit your "Settings" page and scroll down to the "Subscription Plan" section. Click the "Update Credit Card" button to initiate the update process through Stripe.
In the Stripe modal window that will pop-up fill-in your new credit card information and click "Update Card". The process is handled entirely by Stripe. plug&paid will not view or store your credit card information.