Download the window file, then you need to follow these steps:
1 Extract the file and take the game folder from it;
2 Right click on the Mac game icon you have on you HD and, once a pop up menu will appear, click on Show Package Contents and follow the path that will appear: Contents/Resources/Autorun ( if you click on Autorun you will se another game folder inside);
3 Drag and drop onto the Autorun folder the game folder that you unzipped previously, while holding the Alt key on your keyboard ( be careful onto the Autorun folder, not inside it or you will replace the old game folder and the game will not work properly) and release it;
4 Another popup menu will appear asking if you want to merge the files, click yes wait a couple of seconds/minute ( time depends on the size of the file), then once done you're ok and you will have an updated game like I did;
Just a tip for future updates, always look at the script version of the game inside the game folder ( it's a folder called script_version.txt) this indicate the renpy version used to make the game and must be always the same.
In case it's different you can't use the instructions I gave you before, but you need the Mac updated version of the game or, if you have enough power in your Mac, create your own version with the upgraded Renpy engine.
But generally it suffice to wait until it will be leaked here.
Have a good playthrough.