Download and run the setup.exe file for windows. Download and run the Spy-Notify.pkg file for Mac. Extract the Spy-Notify.tar.gz file for Linux and run the .sh file corresponding to your desktop (GNOME or KDE) in your terminal. If you are using a linux desktop aside from GNOME or KDE, you will need to modify either of the .sh files as follows:
Remove line 13 from the shell script, either cp "Spy Notify.desktop" "~/.config/autostart", or cp "Spy Notify.desktop" "~/.kde/autostart". Once you have done this, run the shell script in your terminal as normal. However, you will need to manually add the "Spy Notify.desktop" file to your desktop's autostart forder (or equivalent), to ensure the program runs on startup automatically, once the computer has booted. This will ensure it is monitoring your webcam for activity, without you having to manually run it every time you boot up.