Step 1: First create your private name servers at your domain register or update existing private name servers with the IP addresses you were given in your welcome email.
Step 2: Next login to WHM
Step 3: Click Edit a DNS Zone
Step 4: Select the domain that you have your name servers created for. Ex. ns1.yourdomain.com you would select yourdomain.com
Step 5: Scroll down below Add New Entries Below this Line and enter:
ns1 14400 A IPaddress
ns2 14400 A IPaddress2
Note: Change NS1 and NS2 to whatever you have your name servers created as. If you are using ns3.yourdomain.com and ns4.yourdomain.com you would put ns3 and ns4 there. Change IPaddress and IPaddress2 to the IP addresses listed in the welcome email.
Step 6: Then click Save and the process is complete.