The documentation and setup instructions are included in the downloaded package:

JUser BestBefore Standard and Premium edition
The downloaded zip files is ready to be installed via the Joomla! back-end. If you unzip this file, you will see a file called _DOCUMENTATION.TXT. This is the documentation file for the plug-in.

JUser BestBefore Business edition
The downloaded file must be unzipped first. When you unzip the downloaded file, you will get two zip files: one installation for the component and one for the plug-in. Inside each of these two zip files, you will see a file called _DOCUMENTATION.TXT (unzip the installation file first). These are the documentation files, for the component and plug-in respectively.
In the present version, you will find the documentation files already in the unzip of the downloaded file.