`"No Distractions" for Facebook` works in a very simple manner: it injects a style sheet to facebook.com which locally hides the newsfeed, chat sidebar, and other distracting content on Facebook.
After youo have installed this app, the extension will appear in Safari > Preferences... > Extensions . Here, you can turn the extension off and on - or uninstall it.
If you have any problems, contact me at ulrik.lyngs@gmail.com or create a GitHub issue on the repository github.com/ulyngs/no-distractions-for-facebook/.