Actually, you really need to do it the other way around IMHO
Firstly you need an IP so you register the IPs at your registrar with the appropiate name server.
like 111.222.333.444 = ns1.yournamerserver.com
Then you log into shell and install the name servers for those IPs
Edit the file pico /etc/nameserverips.
The format of the file is IP address = name server. For example:
111.222.333.444=ns1.yournamerserver.com
Just put the IP address that you want to add in the first part and the name of the new name server in the second part.
Please keep in mind before using those name servers that they need to propagate after you registered them with your registrar and usually take 48 hours to do so.
And only then , after being 100% sure that those name servers work , should you edit your DNS for a live domains/hosting account