To add your own nameservers to your VPS, you will need to open a ticket so we can set your Child Nameservers for your chosen domain.
For example, if you wish to use NS1.yourdomain.com, NS2.yourdomain.com, etc, you would need to an IP for the NS1 and one for N2 You will need separate IPs for each nameserver.
You will then need to open port 53 to allow local DNS lookups from your VPS - however, make sure you disable recursive lookups in your DNS software (eg. bind).