Go to https://developers.facebook.com/apps , select Add a New App.
Insert Display Name and Contact Email you want facebook to connect with your website. Then click Create App ID.
Insert the correct Security Check.
Next page, look for product Facebook Login and select Setup.
At Product menu on the left, find Facebook Login and click Settings.And insert OAuth redirect URIs and Save Changes.
**You can find OAuth redirect URIs in your website editor -> Site -> System Pages -> Login, click on Login form to open Login setting, look for Login Callback URL for facebook.
Select + Add Platform to continue.
Select Platform as Website.
Insert your website at Site URL and click Save Changes.
Look for App Secret, and select Show.
Login as admin to your website.
Go to website editor -> Site -> System Pages -> Login, click on Login form to open Login setting, to enable Facebook Login Setup.
User the data of App ID and App secret from number 13 to insert at Facebook Login Setup.