Here are some references for when you decide to add Facebook authentication / permission API to your site. There may be plugins available for this but it’s always a good idea to lean how that stuff works.
General Docs
https://developers.facebook.com/docs/
Setting up auth process
https://developers.facebook.com/docs/concepts/login/
Requesting Permissions
https://developers.facebook.com/docs/reference/login/basic-info/
Requesting Page Permissions
https://developers.facebook.com/docs/reference/login/page-permissions/
Graph API
https://developers.facebook.com/docs/reference/api/
e.g These can all be accessed outside the Facebook environment / logged out
https://graph.facebook.com/cliftonhatfield.page/photos
https://graph.facebook.com/cliftonhatfield
https://graph.facebook.com/cliftonhatfield/picture?type=large
Open Graph Permissions
https://developers.facebook.com/docs/reference/login/open-graph-permissions/
Facebook SDK / code examples
https://developers.facebook.com/docs/reference/php/
https://github.com/facebook/facebook-php-sdk
Enjoy.
