It's not always necessary to register a new domain name when the one you already own will work perfectly fine. Instead of registering a new domain name, you can always create a subdomain using the domain that you already own.
A subdomain is a second website, with its own unique content, but there is no new domain name. Instead, you use an existing domain name and change the www to another name. The subdomain name looks like forums.domain.com, help.domain.com, help2.domain.com (assuming you already host domain.com).
To create a subdomain, do the following:
Log into cPanel and click on Subdomains.
In the drop-down menu, choose the domain in question.
In the box before the domain, type the subdomain name you want.
Click in the "Document Root" box and it will automatically fill in.
Hit the Create button.
To remove a subdomain:
Log into cPanel and click on Subdomains.
At the bottom, under Actions, click Remove.