You can park a domain in your Cpanel control panel under the "Parked Domains" link. A parked domain will resolve to the same content as your primary domain. Please review the cpanel manual for detailed instructions.
You can also multi-host (host an additional website) as an addon domain in your control panel under the "Addon Domains" link. An addon domain resolves to its own domain and content like a separate website. Detailed instructions are provided in your control panel.