To update either the Modding project, of the Map Editor project, first download again the newer version of the project on GitHub, by pressing Code > Download ZIP.
Be sure to make a back up copy of your entire project just to be extra safe now. After you do this, inside the .zip we just downloaded, navigate to OrchidRain_MapEditor\Assets and copy and replace the entire contents into the Assets folder of the Unity project containing your map.
This should make the Unity Editor to recompile all the changes to the code for around a minute. When that's done, you should see all the changes implemented in your project.