Hello,
It seems languages folders on your server doesn't have writable permissions. Fix it, please, the extension use standard Joomla! approach for internalization, but if languages folders don't have writable permission, installator can't install language files. Check the following folders:
<joomla_folder>/language/en-GB/
<joomla_folder>/administrator/language/en-GB/
Set writable permissions for these folders and re-install the module and the plugin. After this you can find documentation in 'Description' field on the module and the plugin settings pages. If you have any difficulties, you can provide temporary access to your Joomla! backend by
email and we'll help you.
Regards,
ARI Soft