Private Name Servers (also called Custom Name Servers) allow you to give your customers ns1.yourdomain.com and ns2.yourdomain.com (and also use these for your own nameservers for yourdomain.com as well).
This article describes how to create Private Name Servers with GoDaddy.com. Depending on whether or not GoDaddy.com decides to change the look and feel of their websites, the steps listed below may vary.
Step 1: Log into GoDaddy by first clicking on My Account on the GoDaddy homepage. On the next page, enter your Login Name or Customer Number along with your Password and click on Login to continue.
Step 2: Click on Manage Domains from the main page to see a list of the domains you have purchased through GoDaddy.com.
Step 3: Find and click on the domain name that you would like to create private name servers for.
Step 4: On the right side, scroll down to the Domain Host Summary section and click on the "+" icon to expand this section.
Step 5: Click on the link "Click here to see details or to modify."
Step 6: Enter the prefix for your first name server (usually "ns1" for ns1.yourdomain.com). Continue by adding the IP address of this name server (found in your Welcome e-mail).
Step 7: Click on Add New Host.
Step 8: Repeat Step 6 for your secondary name server (ns2.yourdomain.com).
Step 9: Click on the Save Changes button and you are done!
You should receive a notification by e-mail once the changes have succeeded. You can then change the name servers for your domain to ns1.yourdomain.com and ns2.yourdomain.com now! You can also give this to all customers that you create in WHM as well!