It's not an update. You have to install it manually. There is a Read Me PDF that will tell you what to do.
You need to put it in Applications/Adobe Premiere Pro CS6/Adobe Premiere Pro CS6.app/Contents/Plug- ins/Common/
When you get to the .app, right click it and select "show package contents" to get to the rest of the path. I found this by downloading the CS5.5 installer, which had the Read Me PDF that was missing from the latest CS6 release.