Hello Johnnatan,
I hope I am understanding you right. I believe you are asking how you would add a cisco IOS device to be monitored by your NMS.
To add a device to a SNMP community: snmp-server community "name-of-desired-community" "RO or RW"
So if you wanted to add a router to the SNMP community "cisco" and allow only Read-Only access you would:
snmp-server community cisco RO
Cheers,
Gabriel