There are many registars in the world with different panels, however we have provided a simplistic explaination of how to register your name servers.
You will have to login to your registrar and find the area where you can specify both of your custom name server addresses as well as where you can associate them with IP addresses on your VPS. Once found, Create NS1 and NS2 entries and assign your VPS IP for those nameservers.
After adding these custom nameservers to your domain registrar control panel, it will take 24 to 48 hous for your domain to delegate authority to your DNS server. Once this has taken effect, your DNS server has control over the DNS records for the domains which use your custom name server addresses
We can also set these up for you. Just open a ticket up and provide the login to your register and the domain you would like it to be setup with.