The Facebook Like Box WordPress Plugin by WPdevart and smplug-in helps you promote pages and post, same as you normally do on the Facebook site itself.
There are many WordPress Plugins for adding Facebook like boxes to a WordPress site. This one is different as it adds more than just a like box. A Facebook Like Box allows visitors to “like” your post or Page content and connect it by sharing on their Facebook site. This Plugin adds a WordPress Widget, a shortcode for embedding in the site’s content, and the ability to actually create popups for Likes and Facebook sharing.
The Plugin is also highly customizable, allowing height and width to be set, languages, and colors. You can also set it as a Sticky box, and show or hide Friend Faces, and other visual elements.
After downloading and activating the Facebook Like Box Plugin, go to Appearance > Widgets to add the Facebook Like Box Widget to your sidebar or other widgetized area of your site like the footer.
You also have the option to use the WordPress Plugin’s shortcode to place into any post or Page to add the Facebook Like Box directly in your content.
Here are some examples of its usage.
This is an example from the Facebook like box that you have added.
The Plugin author has a Facebook like Box demo site so you can see the Plugin in action before you use it.