As far as I know, you can only show multiple places for one PERSON (which could mean two families - one in family as a child and one in family as parent) at a time.
You do this in the Places Workspace. Look at the top of the left panel. You will see that you can list persons or places in the left panel. If you choose people (wait a long time if a lot of people in your file), and then choose one person, you will see all of the places associated with that individual light up with icons.
There are commercial programs out there that will do more sophisticated mapping apps with data from gedcoms.