Click the Download for Windows link. The software will begin downloading. Click on the download icon in the upper-right corner of your browser after download completes. Open and run the file.
Software Installation Help - Firefox
Run installation. Once complete, click Finish
You will be taken to this page after the installation is complete. Click on the Night Shift Launcher icon to open the application. Then click the Open Link.
To start the software in the future, you just need to double click the icon on your desktop.