It is there. First you have to park your new domain and there is a park feature in your cpanel for doing that. Then you have to go into your domain account at your Domain Registrar to change the name servers so that they point to our name servers. The name servers were given with your hosting details.
Bottom line. The domain you asked us to install for you is your primary domain. You use the parked feature to park your "new domain" (which is the secondary domain) and you then get the secondary domain to be directed to your primary domain. So if people use your new domain name they will be directed to your Website, provided of course you have changed the name servers in your new domain account with your Domain Registrar to our name servers. This way you can use both domains.
However, most people ask us to install their new domain as their primary domain. That is usually their first option. You would still have to go into your domain account with your Registrar to change the name servers so the domain is directed to your Website on our server. That makes sense of course. The domain has to be directed to the Website you create. And you can only do that from the account that you used to purchase your domain with. In this case however you will only have one domain.
So you have two choices: park your domain and have use of two domains or ask us to make your new domain your primary and only domain. In both cases you have to change the name servers of your new domain by going into your domain account at your Registrar. The name servers are in your hosting information. There are also some sticky posts in this section that I suggest you READ.