When creating a location, you will see this screen:
Notice that this location does not yet have time groups added:
Cloning a time group means that this location will have the same time groups as another location. Choose a location, then click save:
After saving, click again on the location in the list of locations in the app editor:
The time groups have been added from the location you chose to clone from. You can then add a primary time group from the time group choices. The times will also show up with the location in the app. To put it another way, this is a more complicated "copy+paste" trick.