There are many different ways to find the lat/long for a location. For a single location, you can simply drop a pin on a location straight from the dashboard and the lat/long will automatically populate and you can then adjust your radius.
To find lat/long for multiple locations anywhere on Earth, we suggest using Google Maps. Here's how you can do that in the Google Maps interface:
For more on geofences basics and management, check out our docs on Places & geofences. For help engaging users with Places, visit our Places campaigns docs.