I discussed this briefly on Talk Marketing Now which is an online marketing related channel, and promised to record a video… and so here one is, a little later than I would like.
However it is a very straightforward process and assuming you see Facebook Comments below this post then it worked! You need to install the Facebook Comments for WordPress plugin and then create an App on Facebook at http://www.facebook.com/developers.
The below video will explain it, perhaps better than words. Any questions or comments do feel free to drop them in below!