Setting up Facebook

Create a new Facebook application

Log in to your Facebook account and visit  https://developers.facebook.com/apps/

Click Add a New App

Choose Website as your application type

Skip the wizard

Give your app a name and a category

Complete the Contact Email field. Click on the Create App ID button. 

Configure your domains

Visit the Settings menu Add the domain name of your website to the App Domains box. Then, click Add Platform.

Choose Website from the Select Platform dialogue:

Add your domain name to the Site URL field. Be sure to exactly match the url of your WordPress installation, including http or https:

Configure advanced settings

Visit the Advanced tab and be sure to match up the various toggles with what you see here in this screenshot. Really, that's the easiest way to do it!

Enable Facebook Login via OAuth

Click on Add Product and choose Facebook Login

Be sure the toggles match what you see in the screenshot below:

Add your redirect URI

Paste the redirect URI from your WordPress dashboard into the field labeled Valid OAuth redirect URIs:

Take your app live

Visit the App Review tab and toggle to take your app live. You do not need to submit it for review.

Copy your App ID and App Secret back to WordPress

Test, test and test. Go ahead and log out of your site and give it a test. It should be good to go!