Yeah, it's actually not that obvious how to get it setup. I assumed if I was signed into the other services I'd be good to go, but you have to sign in from the extension explicitly. Once you install the extension, the Start G+ logo shows up next to your picture on the right of the Google bar. Click that sucker to sign into Facebook and Twitter, and then you should be able to check the Facebook and Twitter icons for each post. Lemme know if that does the trick.