If you would like to add a payment method for your account in the payment portal, you will have to authenticate the payment method you would like to use before being able to request your withdrawal.
The payment method you have used previously to make a purchase or pay for a subscription will already be authenticated. It is then shown under saved methods.
Under Add new method you will be able to select one of the available payment methods and then Verify method. During the authentication process, a small transaction will be made in order to finalize the verification. Therefore, it is important that you have some balance on your payment method if you wish to activate a payment method when withdrawing.
Once the payment method is verified, you will be able to proceed with your withdrawal request.
If you have any further questions regarding this, please contact customer support.