If your hosting plan allows multiple domains to be hosted on your account, this then can easily be done inside cPanel.
1: Login to your hosting cPanel
2: Click on Addon Domains, located under the Domains section
3: Enter in the domain in the New Domain Name section
4: Once the domain is entered, click The Subdomain field and the Document Root (usually public_html/domain.com) will automatically fill in. Check "Create an FTP account associated with this Addon Domain" if you want an FTP added. The FTP account would only have access to that specific Addon domain and nothing more.
5: Click Add Domain.