To view your user groups click the "Group" tab at the top of the users screen.
To create a new group click the blue "Add Group" button at the top.
Enter a name for the group and click the blue "Add" button to add it to the user groups list.
Click the blue pencil button to edit the users in that group. Users can be added and removed from the update group screen.
Click the red trash can button to delete that group from the list.