You have to start/create the master name server via the link on the left. then you can setup /register your name servers to point to two ips on the server. then you can just use them for resellers, etc or set them as the default ones.
say your hostname is:
one.domain.com
master dns will set them up as ns.domain.com and ns2.domain.com - you just need to set them to two ips on the server.
sean