Use the [fbinviterlocker] shortcode within your content to enable the Facebook content locker. You will find a button at the top of the WordPress editor which makes it easy to customize and insert this shortcode in to your posts/pages.
You can lock any type of content, such as the content itself, download links, videos, images or anything you can think of. It just needs to be within the Shortcode you generate with the Shortcode creator.
This will be the message that appears in the Facebook invite box when content in your post is locked. You also have the ability to enter a custom message for each Facebook inviter you create.
Select a color for the content locker box. You still have the ability to choose a custom one for each content locker box you create.
Facebook App ID/API Key & Facebook App Secret
Enter the App ID & Key as well as the App Secret of your Facebook Application. You will find instructions on how to create a Facebook Application here.
Here you can set the maximum amount of friends a user will be able to invite at once.
Set the minimum amount of Facebook friends an user needs to invite to get the content unlocked.
Check this box if you want to let your users invite their friends more than one time. Be careful with that, so that your App doesn't get marked as spam.
You also have the ability to post an image with the message to the friends Facebook wall when they get invited by your users. Enter the URL to the image here. Use a proper URL format such as: http://www.yoursite.com/images/image.jpg. You still have the ability to enter a custom image when you create the Facebook Friend inviter locker.