I don't have "Social Network" icons in my Common Library either. Here's what the panel looks like:
This is in Fireworks CS6 for Mac. I believe these are all defaults (no custom folders). I suppose it's possible that a slightly different set could be circulating via the Creative Cloud, or on the Windows operating system. It doesn't seem likely, but I couldn't rule it out either.
Keep in mind that the Common Library can be customized. You can add to it using commands in the Document Library or Common Library panel fly-out menus. Or you can add items directly into the Common Library folder on your hard drive (located in the user library Application Support folder for Fireworks CS6).
FOLLOW-UP: On closer inspection, the Icons folder seems to contain some "social network"-type icons, such as Facebook, Twitter, LinkedIn, Dribbble, etc. Perhaps you can find what you're looking for there.
It could be that your Video2Brain course was based on a beta version of Fireworks CS6 that used a different folder naming scheme.
I am very sorry if the pictures are too little or have bad quality. Is just that it appears like this on the video. This is what I'm talking about.
The icons are the ones that you see on every webpage, the so well known "share icons". I have been trying to find png or psd versions of them on the web, but it's impossible