and have a look at my domain setup.
Each of my designated name servers..
ns73.domaincontrol.com. ['126.96.36.199'] [TTL=172800]
ns74.domaincontrol.com. ['188.8.131.52'] [TTL=172800]
Using this info to query each my chosen nameservers can be done using
dig +short bournetoraiseshell.com @ns73.domaincontrol.com
dig +short bournetoraiseshell.com @ns74.domaincontrol.com
Querying both shows me a 184.108.40.206 IP address. That is my A Record and the IP of my server.
Until both (usually only 2) of your namesevers show the same IP of your VPS, it will never resolve there, or it will about 1\2 of the time.
This A Record is set on the hosts (in my case ns73.domaincontrol.com and ns74.domaincontrol.com) and I do not manage those nameserver hosts, nor do I have any DNS software running on my server. It is not necessary to install any dns software
to make these point to your VPS IP.
The task at hand for you is "I need to Update my A Record to <IP_of_VPS> on all of my nameservers."
Whois is your Domain Registrar?
Ultimately, you may need to tell us (here, or me via PM) the name of the domain to help you further.