If you use ISPmanager as ns1.mytest.net. ns2.mytest.net, you will need 2 ip-addresses for name servers.
Log in to ISPmanager --->Domain names --> Records --> Add 2 A records for mytest.net
ns1.mytest.net - 193.124.179.43
ns2.mytest.net- additional IP address
Then you need to login to your domain registrar's client area and create 2 A records according to the above names and addresses.
This is only one variant, you can choose other variants
https://doc.ispsystem.com/index.php/..._configuration