You can set your custom/private nameserver from WHM

1. Login to your WHM

2. Go to Server Configuration » Basic WebHost Manager Setup or type “Basic” in the search box and it will display the Basic WebHost Manager Setup option. Click on it.

   

3. Under Nameservers, Select Explicitly Set the Nameserver and enter or change the nameserver in Nameserver 1, 2 field. Then, click on Save Changes.