If you wish to give your clients reseller status, which will allow them to have their own branding and set of clients, you must enable their admin console.
In the Clients tab, hover your mouse over their account and select Enable Admin Console
You will see a confirmation message. If they have not yet enabled a domain, give them a temporary URL similar to the one you first received. This means that until they create their own domain and configure their DNS settings, their service will be hosted on your site.
Remember, once you enable someone as a reseller, that change cannot be undone.