The Domain of One's Own Servers page is the interface where DoOO Admins can manage cPanel/WHM servers connected to their DoOO instance. This page is in the WordPress backend to ensure that only logged in users (DoOO Admins in particular) are able to access it, and can be found at /wp-admin/admin.php?page=dooo-servers. For example, on stateu.org, the page is located at: https://stateu.org/wp-admin/admin.php?page=dooo-servers.
Clicking Login will take you to WHM. Clicking Default will change the default server where new accounts are created.
Servers may only be added/removed/edited by Reclaim Hosting, but DoOO Admins have the ability to log in to servers connected to their instance, see account numbers per-server, and set one as the default server for new account creations if there is more than one server.