In order to use FB comments you need to first Sign Up as a Facebook developer (https://developers.facebook.com/apps) - using your Facebook username and password. Then click the "Create New App" button. Enter a name for the application in the "App Name" field. Enter your domain name in the "App Domains" field. After you complete the form to register your application Your App ID will be visible, but your App Secret will be obfuscated. To reveal your App Secret, simply click the “Show” button. Be sure to copy down the App ID and App Secret – you’ll need to enter these settings to use the plugin.