Facebook

First, you'll need to register an app with Facebook and get an App ID and App Secret.

To create a Facebook app, login to https://developers.facebook.com/, in the top-right, you can click "My Apps", then "Add a New App."

Once created, you'll be taken to a "Product Setup" screen. Find the entry for "Facebook Login," then click "Get Started."

On the settings screen for Facebook Login, make sure "Client OAuth Login" and "Web OAuth Login" are enabled. Under "Valid OAuth redirect URIs", you'll need to type in the URL to your Multistreamer install, with /auth/facebook appended to it, ie:

https://example.com/auth/facebook

or

https://example.com/<some-prefix>/auth/facebook

if you're running Multistreamer under some prefix.

Once you've gotten your App ID and Secret, add them to the facebook key of the networks table, ie:

...
networks = {
  facebook = {
    app_id = 'app_id_goes_here',
    app_secret = 'app_secret_goes_here',
  },
},
...

A few notes:

Your Facebook app's posts won't be visible to the public until you make the app Live. Once Live, any posts made by you (the admin of the app) will be visible to others. This applies to your own profile, pages you're an administrator of, and so on.

If you want your app to be usable by other people, you have a few options:

Option 1

Write and publish an app privacy policy somewhere and generate an app icon. Once you do this, you will be able to submit your app to Facebook for App Review, and once approved, anybody will be able to use your instance of Multistreamer.

Option 2

If you have only a few people who will be using your instance of Multistreamer, you can assign them the "Tester" role within your app. This does require the user to have a verified Facebook account (if I recall correctly, this means Facebook needs their phone number). After adding the user as a Tester, they'll need to login to https://developers.facebook.com/ and accept your invite to be a tester of your app.