Open your Google Maps application on your phone. Click on the Menus button and select "Your Places" from the list.
Select "Maps" on the Top Bar and then select the Umphreak's Anonymous map overlay that you are looking for.
This next screen will show all the overlay icons for the map and a brief rundown of the title and description.
Now when you are in Atlanta, just using your Google Maps application like normal, you will see the Atlanta icons overlay show up on your standard map. This makes it easy to know if you're close to several things at once, passing by someplace you didn't know about, etc.