With Facebook Login option, you can provide your customers with a secure, fast and convenient way to log into your website without them having to create a password. To get started, visit https://developers.facebook.com/
Create or enter your account on Facebook for developers and click Add a new app:
Add display name and contact Email -> Click 'Create App ID':
In the Products section add a new product and click 'Set up' at Facebook Login.
Go to Products -> Settings in the left sidebar and add your website URL: yoursitename.com/userlogin/?social-login=facebook in the Valid OAuth redirect URIs field and click Save changes (you may leave all other fields blank).
Add your App domains:
Go to your top panel and make your website public by changing your app status. Use the toggle switch.
Paste App ID and App Secret in your WP admin area: AliDropship => Settings => Accounts.