To create groupings, you first have to create at least one group. Once a group has been created, go to:
Settings > Users > Groups

The page displayed, is the same, as the one used to create groups. But to create groupings you have to first select Groupings option on top of the page (see picture 6).
Picture 6

When Groupings have been selected, there is only one option available, Create grouping button. When that is selected you will be directed to a page called General, where you have to give the grouping you are creating a name. Once saved, you will be directed back to the Groupings page (see picture 7). Now that the grouping has been created, you must add groups to the grouping. That is done by clicking on the heads under the Edit bar (as shown by the red arrow on picture 7).
Other options available under the Edit bar, are Edit (the pencil) and Delete. If you want to change the name of the grouping click on the pencil, and if you want to delete the grouping, select delete.
Picture 7
To get an overview of all the groups and groupings, simply go to Overview bar on top of the page.