How to register your child Nameserver/private nameserver/ hostname:
As you are a reseller, You can use your own nameserver for your clients. For this, you have to register your nameserver from your domain control panel. If your domain is with us, we will register your nameserver. But if you have domain from any other hosting providers, they will help you to register your private nameserver. We have given tutorials for three major domain registrars. Others will have almost the same options.
Nameservers:
ns1.yourdomain.com 166.0.175.13
ns2.yourdomain.com 166.0.175.14