UPDATE: As of OptimizePress version 1.0.16 we now have Facebook comments and like buttons, so the following should no longer be needed, however we'll leave this here for reference.
Note: We have plans to add our own Facebook comments element in the near future...
If you wish to add Facebook Comments to your pages, you can use the Facebook codes directly from their website
You can get the code from this page (you'll need to complete a few details there):
You can add both of the code snippets in the HTML element on your OptimizePress 3.0 page
If you need any further help with this, please let our team know