There are 9 steps to get it done.
1. Sign in to Facebook and go to https://developers.facebook.com
2. Click My APPs, then click Create App
3. Select Consumer, click Next
4. Fill in the form as follows, then click Create App
5. Click Set Up as follows
6. Click setting on the left
7. Fill in the form as follows, you will need two URLs as the Valid OAuth Redirect URIs, it should be
Don't miss the slash at the end.
Then click Save Changes
8. Click Settings -> Basic on the left. Follow the steps shown in the screenshot as follows
In (2), (3) and (4), you can fill in the URL of your terms and conditions, it should be https://yoururl.com/generic/terms_conditions
For (5), click Save Changes.
For (6), switch to live.
For(7), here are the APP ID and APP Secret that you need to paste into the script.
8. Copy the APP ID and APP Secret, Sign in to the script as the super admin, go to Global Setting -> Auth Integration, go to the Facebook Login block, tick Enabled and paste the two credentials
Click Save Changes.