In order to use your own domain name at JustHost, you should change the name servers to the name servers of JustHost.

The following is JustHost name server information:
NS1: ns1.pipedns.com
NS2: ns2.pipedns.com
NS3: ns3.pipedns.com

You can find these information in JustHost hosting welcome email.

JustHost hosting allow you to host unlimited domain name.  You can view JustHosting hosting features from this blog Introduction to JustHost Hosting Plan. If you want to addon domain to your JustHost hosting account, you should change the name servers of addon domain to the name servers of JustHost.

For more detailed information of JustHost, you can visit JustHost.com