Create an account as you normally would. Then go to edit resellers and give them reseller privliges. After that go back into edit resellers and edit their access. On the bottom of the access screen you will see text boxes to add their name servers. All you do is add them there and have them register them at their registar. One thing you may want to do is edit the DNSzone for their domain and give a seperate IP for each ns line. Some registars allow them to have the same IPs while others complain non stop about it. Although this is your choice I suggest giving them seperate IPs.
