WPM Globe Edition was designed to use the classic Unity input system (like Input.GetMouseButton methods, etc.). In order to support future and new input systems, the asset has decoupled this usage so all methods are included in a single proxy class, called DefaultUnitySystem.cs. This class implements the interface IInputProxy.
You can therefore implement a new class which implements such interface or create a new class that derive and override the methods of DefaultUnitySystem class, so you provide your own input logic for common tasks like getting the key or button pressed.
The DefaultUnitySystem.cs class can be found in the folder WorldPoliticalMapGlobe/Scripts/Core/Input.
Once you have created your own class, you can just assign it to World Map Globe Edition component at runtime like this:
WorldMapGlobe map = WorldMapGlobe.instance;
MyCustomInputSystem newInput = new MyCustomInputSystem();
map.input = newInput;