To provide flexibility there are two levels of grouping provided, Users and Groups.
Creating a Group
Select Groups from the left hand menu - Then Click on the + Icon to create a group
Now give the group a name and press Save
Creating a Sub Group
Select the Group that the sub group will be placed under - Then Click on the + Icon to create the sub group
You will see the Group where your Sub group will be placed under, give the subgroup a name and press Save
Removing a Group or Sub Group
Select the Group or sub group that you wish to remove - Then Click on the X Icon to remove - confirm deletion.