Here is a step by step direction, and you will need IPs for this to work.
Go into your WHM, click the link to show &IP address usage&, from the left menu.
This will show you what IPs are free to use, because there is no site info listed to the right of them.
Now, find 2 IPs that do not have sites listed on them.
Click on the &Show/Edit Reserved Ips& link from the left menu.
Now, go down the list of IPs, until you see the two IPs you are going to use for the resellers name servers. Check the check box for each one, then go to the botom of the page and hit the submit button.
assuming that you do not use SSH to manage your zone files,,,
You want to click the &Edit a DNS Zone& from the left WHM menu.
Select the resellers domain from the list, and click the &Edit& button.
Now, you see the resellers zone file.
BE CAREFULL IN HERE - This file makes their site work!!!
Look at the Zone file.. your second line should be an entry box full of numbers, and the words &Serial Number& off to the right of that.
You need to add the count of 1 to the serial number in that editable box.
(Example: 1009665039 will become: 1009665040)
Now, go down the list of editable boxes in the zone file,,,, several lines later you will see &Add New Entries Below this Line&
There are some blank boxes to edit in new info.
Put the following:
In the first box, put NS or what ever name you are using for the name server, but just NS for this example.
NS then leave teh numbers 14400 alone,,,
after the word &IN& you want the letter &A& in that selectable list to show.
In the first editable box after the letter &A&, put in the IP numbers that you selected from the list of available IPs.
Repeat this with NS2 for the second name server on the next line.
Now click the &Save& button at the bottom of the page.
Send an e-mail to your reselelr to go to his registry with the new IPs for the name servers,,, make sure to spell it out for them...
ns.reseller.com - IP:xxx.xxx.xxx.xxx
ns2.reseller.com - IP: xxx.xxx.xxx.xxx
Now, you can go into your Edit reseller area of the WHM, and select that reseller.. go to the bottom of his page, and enter the names for his new name servers... ns.reseller.com etc...
click to save.
by reserving the IPs from the edit reserved IP list,,, your resellers name servers won't come up to someones site if entered into a browser by IP number to see where they go. People do that...
if your using shared IP hosting, and only have a couple IPs per server... you need some other person to tell you if or how to set up the name servers.