4 - Login Facebook
Follow the steps to create a Facebook APP: https://developers.facebook.com/quickstarts/?platform=web
Create an application with the name you want
Write the captcha
Choose session start with Facebook
Fill in the form data
Fill in these data, they are important
Configure the options as they come in the image, in the field of "URI of valid OAuth redirection", paste the value that you have in the Admin in the section Setting-> Social login "Facebook Callback URL"