Google will be delivering Android 4.2 updates to owners of its Galaxy Nexus and Galaxy 7 devices over-the-air, and likely very soon, but if you’re just not able to wait, there’s a way to update manually right now using firmware downloads found on Google’s servers. You’ll need to have the GSM version of the Galaxy Nexus for this to work, and any version of the Nexus 7 tablet.
This doesn’t necessarily have to be that difficult, as the official ROMs you’ll need are readily available on Google’s servers. You can grab the one for the Galaxy Nexus here, and pick up the version for the Nexus 7 here. Installing both still does require dealing with some potentially intimidating backend tinkering, however, so if you’re not that comfortable or you haven’t used a tool like ClockworkMod’s ROM manager before, you may want to hold off until Google gets things served up the easy way.
Jelly Bean 4.2 is an incremental update from Jelly Bean 4.1, and brings a number of features, including a new photo sphere panorama style software camera, multiple user accounts on tablets, a new quick settings section, improved Google Now, Miracast support and more. The update should be delivered to the Nexus family of devices sometime in the next couple of days.