VPS servers are different than shared web hosting. As you have an entire dedicated space, you have to create your own name servers. To perform that is very easy to do.
Step 1: You have to grab your VPS IP address which you can find from the 'server information details' which emailed to you when you did sign up
Step 2: Go, and login into the control panel of your domain provider, and from there, create two name servers for your domain name
example:
ns1.yourdomainname.com IP: 1.1.1.1 (VPS IP)
ns2.yourdomainname.com IP: 1.1.1.1 (VPS IP)
That's it :)