Navigate to the plugin configuration page, click the "Add New Provider" button (located either in the middle or top-right corner), select Facebook as the application, and copy the callback URL from the plugin and keep it handy, as you'll need it to configure Facebook as the OAuth provider.
To perform SSO with Facebook as Provider, your application must be https enabled.
Login to Facebook Developers: Go to Facebook Developers and login with your account. Select My Apps from the menu:
Click on Create App and select For Everything Else option.
Name your application : Provide a Display Name and Contact Email for your app and then click Create App ID button.
Setup Facebook Login : On the PRODUCTS page that follows, click on Set Up next to
Facebook Login.
Next choose the type of application, for this tutorial we have selected Web.
After clicking on Web go to the Settings tab under the Facebook login.
The Client OAuth Settings page for Facebook Login will appear:
Enter the Callback URL (copied from the plugin) in the Valid OAuth redirect URIs field.
NOTE: Before entering the callback url it should be changed to https.
Click On Save Changes.
Go to Settings->Basic and Enter your Privacy Policy URL in the Privacy Policy URL field. Click on the Save Changes button to save your configurations.
Get App Id and App Secret : Click Settings in the left nav. On this page you can retrieve your App ID and App Secret.
Click Show to reveal the App Secret (you may be required to re-enter your Facebook password).