From the top menu choose "Groups" then "Locations"
Once on the Location page, you can click on any location and it will bring you to the location list page.
Then just click on any location and this will bring you to the location detail page where you can see the Groups and Members associated with this location.
To create a group that will belong to this location, simply click the "Add Group" icon.
If you have a pre-existing group, you will need to go to that groups setting page and assign it to the location you desire.