The plugin’s options include automatic inclusion of the comments box in posts and/or pages…
or you can selectively include the box by using the shortcode: [ fbcomments ]
This plugin works independently of the WordPress comments system, which is nice because it won’t bloat your comments database and it gives you more options. You can add the FB comments box in conjunction with WP comments, or in place of it.
If your visitor is logged into Facebook this is the result:
Powered by Facebook Comments