In the back-end, you as a website owner can type any URL that you want the visitor to share with their facebook friends. A modal window will show up in the front-end with a facebook share button. If the visitor chooses to share, then the URL you typed in the back-end gets shared. If the visitor does not want to share, then he can simply close the ‘Share the link’ dialog box.
Activate the plugin through the plugin page, there no need to do anything else. Here’s a link to the YouTube video on how to use the plugin –