To access the master reseller panel for creating sub reseller go here: http://www.mellowhost.com/master
The panel will ask for email address and password. This email address and password is the same you have used in our billing to order the package. Usually you have to use them to login to your clientarea and pay the invoices, updating account info, support ticket management etc.
Clientarea is located here: http://www.mellowhost.com/billing/clientarea.php