In previous iterations of Windows Server Update Services (WSUS), your group policy would point to your WSUS server with the following:
But now, with WSUS in server 2012, you have to specify the port number. The port number is 8530. So in your group policy, you would specify the following:
Once you have refreshed your local group policy or allowed it to apply itself overtime, you will then be able to receive updates from your local WSUS 2012 server.