Updating Your Payment Method
Updating your payment method is within your account panel. To get here, click the button in the top right corner of your screen and then click "Account". Once you are in this screen click "Billing".
Here you can view or edit your subscription details, view past invoices and update your payment method. If you have not added a credit card yet it will have an orange "Add Credit Card" button and you can click that and fill out the info to add your first card.
If you already have a card added, it will show the current card info and the current email listed that invoices and receipts will be sent to. To edit these, click the pencil next to the information you would like to change.