How to create name server in Plesk?
Make sure DNS server is installed by running Plesk autoinstaller:
Add record for domain by following path: Domains -> example.com -> DNS settings -> Add record
NSas record type,
NSserver you need to create. Click OK button.
Arecord for your name server. Click Add record .
Aas record type, type your name server as domain and related IP address. Click OK button.
At this point, the nameservers are configured on your server, and you will need to register the nameservers with your domain registrar. Please refer to your domain registrar for further instructions on how to do this.
Please also check the official guide for you reference.