bgmaster you can place the IP 123456789 on records, then on the name servers you use the other IP on ns2, for example:
ns1.domain.com - IP 123 456 789
ns2.domain.com - IP 123 456 788
Regarding the DNS Manager... You should have a list of IP's in there, if not, please push the Fix option on the top menu of your aaPanel, if that does not work, restart it after, then login and try again.