The Audience Network allows you to monetize your websites with Facebook ads. This guide explains how to enable Audience Network demand for Video on Desktop and Mobile Web sites and Display for Mobile Web sites only.
Audience Network for Mobile Web Display is currently only available to select publishers via header bidding. Therefore, you may not have access to this feature in your Facebook app settings.
Guidelines on how to enable AN video demand to monetize your video content
Header Bidding concepts to guide you through success on Audience Network
Guidelines on how to setup the AN adapter with the Prebid Wrapper
Instructions on enabling the native format within Header Bidding
Instructions on enabling the fullwidth format within Header Bidding