Fender's free guitar-focused Studio recording app/amp sim (Studio) is handy indeed for quick takes and practice, though it ...

Open your Facebook app and tap Menu in the bottom right corner. Tap the gear icon in the upper-right corner. You can also scroll down to Settings & privacy and then navigate to Settings.

If you're worried about privacy, a webcam cover could make sense. But it could also break your MacBook's screen, and built-in macOS and hardware features mean that you don't need one anyway.