To start with, use the link below to setup a facebook app.
On all apps click & create a new app. Fill in the next information & use consumer as app type. You will be redirected to the dashboard once these information are filled out.
Add a new product Facebook Login. Once you click setup on Facebook Login, you will be redirected to the quickstart page.
You can locate the quickstart page from the dashboard menu under Facebook Login menu. Click on the quickstart menu. The page on the image below should be brought up. Click on Web & fill in the following information.
Locate & click the settings page from the dashboard under the Facebook Login menu.
Once you are in the settings page under Facebook Login, fill in information in the page.For the Valid OAuth Redirect URIs Field use the following url format. Replacing example.com with your site url.You can also find the callback url on your script admin settings on the tab social login.
With that done you will need to copy your facebook App ID & App Secret. To do that, you will need to navigate to the menu basic under the the menu Settings.
Once in the basic page, you will find your facebook App ID & App Secret. Copy them.
Paste the copied App ID & App Secret in your script admin settings on the tab Soical Login.