Log in to the control panel as admin.
Suppose we have two IPs:
111.111.111.111
222.222.222.222
Go to "WEB → Domains "
Create a default domain in your admin account, for example example example.com
Go to "DNS ". Create a domain name and specify the primary IP
Click Advanced Options and create two NS entries
Record : ns1
Type: A
IP or Value: 111.111.111.11 (i.e. main server ip)
In the same way, we create a second NS
Record : ns2
IP or Value: 222.222.222.22 (your extra ip)
The domain registrar, write the following data for your domain: example.com
NS1 ns1.example.com IP 111.111.111.11
NS2 ns2.example.com IP 222.222.222.22
After this you can write in all domains
ns1.example.com
ns2.example.com
as in the panel and at the registrar.