To install this add-on, first download the zip file from your purchase receipt and save it on your computer. Do not unzip this file.
Login to your WordPress site and go to Plugins > Add New and click Upload. Upload the zip file from your computer and click Install Now. Then it’s ready to activate.
The settings page for the Authors add-on is located in Books > Settings > Add-Ons. There’s a section on that page for “Authors”.