Google has already started to deliver the new Android 4.3 Jelly Bean operating system to the owners of Nexus 4 and Nexus 7 devices out there, yet it will take a while before all users can enjoy its benefits, that’s for sure.
However, those who would like to grab the update before it is officially pushed to them can already do so, as the necessary builds have already emerged online and are available for manual downloads.
However, they should keep in mind that they will need to have stock Android 4.2.2 (JDQ39) running on their devices to install the new software, as droid-life notes.
Those with stock, non-rooted devices will have to install the update via adb sideload, or via a custom recovery. Those with rooted devices and custom recovery will install it as any other package.