If it's a school issued computer it won't work right away. It'll say "From an unidentified developer" or something. So, after opening the zip file, a folder appears. Open it and pull out the app that says "Shadows." Next, right click on the app and open package contents. Copy "Contents." Create a new folder, titled whatever, and 'Paste item" (Command c, command v works fine.) Next, rename the folder to whatever.app and click add. Then you have to drag it back to the folder and open it from there. :) Hope this helps.