In order to monitor and get reports for group of Host's/IP's, create a network object for that subnet. Follow KB article 000001997 to create a network object.
Once you create a network object for your desired group of Host's/IP's, navigate via Monitor > Subnet to monitor and extract reports for that subnet.
Note: Single hosts can be monitored navigating via Monitor > Hosts as well, Also monitoring internal hosts is enabled by default, In order to monitor external host/group of host's make sure to enable external host monitoring. All the details for that is present in KB article 000001066