It is specially designed to work with WhatsApp.
How does it work?
1. First enable the developer settings on your device (on older versions it is not needed).
To enable the developer settings go to settings > about phone > and click on the android version about 7 times. If you have this setting go to step 2.
2. In the developer options enable mock locations.
3. Set your location to be 'device only' (use only gps location).
4. open the app and now you can set your location where you want.
NOTE: This fake location app might not work with some apps, but it works with whatsapp.