On free hosting, I believe you are able to host up to 2 additional Addon Domains and 1 Parked Domain. Addon Domains allow you to host separate websites on each domain, while Parked Domains show the same website as another domain. To set one up, click on either the 'Addon Domains' or 'Parked Domains' buttons in cPanel, and fill in the information. The 'Domain Root' is the path to what the domain will be pointed to; there is no need to set a 'Redirects To' unless you would like your domain to redirect to another. You may not use one of the x10 standard domains: .x10.mx, .x10.bz, .pcriot.com, .elementfx.com, .exofire.net.
Once you have added your Addon/Parked domain, please go to your domain registrar's website and add the following nameservers to the domain that you signed up for or bought:
ns1.x10hosting.com
ns2.x10hosting.com
Then please wait 24 hours.