1. Download a copy of the plugin here

  2. Extract the downloaded zip file and move the resulting timelapse+studio.lrplugin folder to a location on your computer you can remember (like the documents folder)

  3. Open Lightroom and go to File -> Plug-in Manager...

  4. In the Plug-in Manager, click the "Add" button on the lower-left and select the timelapse+studio.lrplugin from the location determined in step 2

  5. Close the Plug-in Manager, then go to File -> Plug-in Extras and select "1: Group Photos by Time-lapse". On the first use, this will open the activation dialog where you can start the free trial or register.