Important note for Mac OS users only - Catalina and later
Because recent changes to Mac operating system permissions can block this plugin's built-in Exiftool component, it is recommended that you install the Exiftool application separately. This is freely available at Exiftool and the package (DMG) is a standard Mac installation.
The plugin should then detect it automatically.
Unzip the download. You should now have a plugin called 'xxx.lrplugin'. If your unzip program didn't keep this parent directory, then you should create it and copy your unzipped files into it.
The plugin is installed via the Lightroom plugin manager.
If you have donated towards the project you should unlock the trial version using the registration code that you should have received.