It does take a little bit of time to set up. First you have to create a new app at https://developers.facebook.com/ and then configure it, which was pretty much self-explanatory even for a non-developer like myself, then you set up the plugin, which is fairly simple to do.
At first I thought the Like Box wasn't included but it is included as a widget which can be found in Appearance > Widgets. There are a few other widgets from FB too.
Assuming I didn't make a mistake when creating the app, it is buggy.
In the settings, when I choose where I want a button to display e.g. pages, posts, etc, then I save the settings, I have to choose and save again because the plugin clears my choice.
A similar thing happens when I try to set a valid FB page URL for the Like Box and Follow Button widgets. When I save, the URL doesn't get saved, resulting in the Like Box not displaying.
I have tried this with all other plugins disabled, and it's still not working as intended.