You can allow external web servers (hosts) to access your MySQL databases by adding their domain name to the list of access hosts that are able to access your MySQL databases. localhost is the server that your site is currently on.
From the dashboard, choose a domain. Click the Advanced tab and click the databases link. Click the access hosts link under the database. Click the create a new access host link. Enter the name of the host you wish you create in the format test.domain.com.