You need to use a Facebook Comments code if you want the comments to be shown on sidebar. To do this
1. Please go to https://developers.facebook.com/docs/plugins/comments/, and look for Comments Plugin Code Generator.
2. Configure the fields as you deem fit. But, I strongly recommend using the URL of your blog on URL to comment on field and 318px on width field.
3. Click on "Get Code" in order to show the form codes.
4. Copy the first code and paste it to your site's WordPress dashboard >> OptimizePress >> DashBoard >> Analytics and Tracking >> Other Tracking Codes field.
5. The second code goes to WordPress dashboard >> Appearance >> Widgets >> Text widget
That should successfully show your Facebook comments on blog sidebar.