by assigning the hosts to groups automatically (Hosts → Auto assign)

by specifying the default groups in the ICB (Initial Configuration Block) distributed during the initial deployment of Management Agents (Hosts → Manage ICBs)

In case you are installing Management Agents to a known group of hosts, you may define a specific ICB containing the predefined grouping for these hosts in the management system. See Creating ICBs.

by assigning the hosts to groups manually (Hosts → Manual grouping)

This is viable if the amount of hosts is small and there is no possibility to use the alternative methods described above.