Hello,
Thanks for the question. Adding a second domain to your account is actually very simple. You first need to register the new domain name, make sure that it's pointed to our name servers, and then add it as an add-on domain in the cPanel. Please refer to the tutorial: How can I add another domain name to my account? It summarizes the steps and different options than can be done in adding a domain to your account.
I hope this helps to answer your question, please let us know if you require any further assistance.
Regards,
Arnel C.