You can add a new group by clicking 'Add group' in the right top corner.
Add a group
When you create new groups no dashboard will be visible. You can add the standard dashboard by going to 'Dashboards' in the Configuration menu.
You can assign devices to a group under by clicking 'Assign devices' in the tab 'Sub-assets'. You can also add a subgroup here by clicking 'Add group'.
You can delete a group by going to the Groups and click on the 3 dots at the right corner of the group tile.
Deleting a group