Note that adds the folder "Shared" on your hard drive to the Side Bar. That is the folder where you share things between the Users (accounts created) on your computer.
If you were missing the Shared heading, which lists servers and computers shared over the network, go to Finder > Preferences... and make sure at least one of the items under "Shared" is checked (Back to My Mac, Connected Servers, Bonjour Computers). If none of those are selected, the Shared heading goes away.
Ivan