You can actually login to your WebHost Manager prior to setting up your domain name and nameservers, but it's good to get your domains setup properly right away.... because of the 24-72 hours it takes for those changes to take effect.
To access your WebHost Manager interface, enter:
or prior to domain (DNS) propagation, enter:
(where YOURIPADDRES would be for example, 18.104.22.168; see your welcome email for the IP address you should use).
Accept the certificate, then use the username that we provide for your master reseller account username and your cPanel password you had on your primary domain