First of all, there are 2 types of “adding new sites”:
Parked Domain
“Parked domain” means that the new domain will work perfectly the same with the old domain (or sub-domain).
Example: you currently have yourname.sitefrost.com. Then, when you add a new “parked domain” (lets say it’s yourname.com), accessing yourname.sitefrost.com/index.html and yourname.com/index.html will show the same page.
Add-on Domain
“Add-on domain” means that you’re adding a completely different site (a new website).
So, accessing yourname.sitefrost.com and yourname.com will show a different site.
The new site can be placed in a different folder/directory. If yourname.sitefrost.com’s root path is /home/yourname/public_html, yourname.com’s root folder’s path can be set in a different directory (such as: /home/yourname/site2).
How to do it?
Both of them can be done via cPanel (url: http://www.sitefrost.com:2082) by clicking “Addon Domains” or “Parked Domain” (select one).