The option you're looking for is "mock location," and it is buried in the developer options in the settings menu on your phone.
You will probably have to enable the developer options menu on your phone, which is done by tapping the build number in "about phone" five times. You will get a popup message when developer options are enabled, and then the Developer Options entry will appear under "System" (at least on recent Android versions) in your settings menu.
Note that this is not a complete solution. You still need a mock location app, which you will give permission via this screen to override your phone's reported GPS location.

