There are a few steps that you must do to prepare yourself to host more domains (resold hosting accounts).
Setup Private DNS:
If you ordered the private nameservers, then before doing anything else you must setup your private nameservers.
Before creating a hosting account for a domain, the domain must be registered and pointed to the proper DNS.
We do not register resold domain names, but we do offer an optional Enom.com reseller account for you to register/manage your resold domain names.
Setup Hosting Packages:
Web Host Manager (WHM)allows you to create any number of packages. You can decide the disk space, monthly bandwidth, number of email accounts, etc. per package. Please check this tutorial on how to setup your packages.
Setup hosting account:
Please check this tutorial on how to use your Web Host Manager (WHM) to create a hosting account using the packages you created in the previous step.
If you registered and pointed the domain correctly, then the created hosting account will be up and ready to go.
You may read more tutorials about WHM functions.