You can update your Verified Address on this page. Once there, click the "Edit/verify your address" link, update your address, make sure the "send a postcard" check box is checked, and click the blue "Update" button.
You do not need to make an additional payment to do this. A new postcard will be sent to your new address within a few days of doing this and should arrive in a few weeks.
If you need further assistance, please feel free to contact us directly.