You can download the July 2012 update (KB2703187) for VS2012 RC from http://go.microsoft.com/fwlink/?LinkID=257044. More information about this update is available at http://support.microsoft.com/kb/2703187.
As with Visual Studio 11 Beta, you will also be notified via Extension Manager. We did, however, make a change for RC to check for updates periodically. This will improve the end-to-end experience for VS updates.
As always, we’d love to hear your feedback. Should you have any problems installing the July 2012 Update for Visual Studio 2012 on RC (v11.0.50522.1) please download and run our log collection utility and visit our forum or file a bug on Microsoft Connect.