You can create groups by navigating to Settings > Groups. Groups can be assigned as 'viewable groups' to users added without admin privileges. This restricts the viewable data to that user by their specified viewable group.
ActivTrak will also recognize Active Directory groups if the workstation is assigned to a group. Workstations assigned to an Active Directory group will only create the 1 group in ActivTrak to which it belongs. For more specific answers regarding Active Directory groups, please create a ticket.
To learn how to create groups and assign users to those groups, check out the tutorial below.