Before starting your session, you will always be notified which payment method is going to be used. You can change this selection by pressing the "Change payment method" button.
This selection will list all cards previously entered into your account, and the final option is "New payment method". Choosing this option will redirect you to the billing information page, where you choose card or PayPal and enter the required information. This is also the page you're redirected to when setting up your account for the very first time.
Please note that in order to remove a credit card from your account you will need to contact our support team by clicking here.