Firstly, unlike monetizing with AdMob, Facebook requires the URL of your published game before you can monetize. This means you need to upload your game to Google Play before you can monetize with Facebook. Once your game is live on Google Play, follow these steps and release the new monetized version onto Google Play.
Are you unsure on how to publish a game to Google Play? We have a helpful video tutorial.
1. Log in to your Facebook Developer account.
2. Select “Add a new App” in the dropdown menu
3. Create your App ID
4. Add "Product" and Select "Audience Network"
5. Enter the Google Play URL for Your Game
6. Create Add Placement
7. Select and copy “App ID” and “Placement ID”
8. Paste these fields into QuickApp Ninja, ’Generate’ Your Game and Upload to Google Play
Not sure how to upload to Google Play?
We have a helpful video tutorial, here