InDesign CS4 or later

1. Open your Script folder in Explorer/Finder.
   You can do this from InDesign, using the Reveal in Explorer/Finder menu item of the Scripts palette.
2. Remove any previous installation of TGI.
   Assuming that only TGI occupies your Version 4.0 Scripts folder, delete your Version 4.0 Scripts folder. 
3. Expand the Version 4.0 Scripts.zip archive, so that you have a folder named Version 4.0 Scripts;
4. Copy/move the Version 4.0 Scripts folder into your Script Panel's folder.