If you have an active subscription, or if you have cancelled your subscription but your subscription period is ongoing, you can update your payment method from Account > Payment Settings.
If your subscription period has ended, you can update your payment method at the time of checkout when purchasing a new subscription.
In order to change your payment method, log in to your account on the site. Once done, click on the avatar icon and then click Account. This will take your to your account settings page.
Click the Payment Settings link next to your price plan to update your payment method.
The changes will take effect immediately and you will be charged against your new payment method on your next billing date.