There is indeed. Mac file structure is kinda dumb when it comes to apps. It's hidden in Contents/Resources/autorun.
Mac Instructions:
- Drop the ".rpa" file into WorldsCrossingAcademy-1.6.0.x-mac/WorldsCrossingAcademy.app/Contents/Resources/autorun/game folder
- Open "WorldsCrossingAcademy.exe" and once you start or load a game, you should get a chime and a notification thanking you for purchasing the DLC.