Add or change your payment method through My Account -> Payment Method -> Add. From there, just add the relevant payment details:
Log into your account, then simply click My Account on the top right hand corner of the page
Select Payment Method. The amount of payment options available to someone will depend on their country of registration
Simply then choose your desired payment method
Please note, if you are experiencing difficulties with registering your new payment method, simply contact our Support Team who will be happy to help.