Take note of your Facebook app ID and secret (apps can be created at developer.facebook.com);
The Facebook app must have been submitted to Meta for app review with the “pages_manage_metadata” (to retrieve Page Access Tokens for the Pages, apps that the app user administers and set a webhook) and “pages_messaging” (to send messages) permissions.
In order to integrate a Facebook Messenger app you must acquire a Page Access Token from your user. Once you have acquired a page access token from your user, call the Create Integration endpoint with your app secret and ID and the user’s page access token.
A Facebook App ID.