To download and install Jelly Bean 4.2 on an Android device, manually update and pull the download from the server. This only works on devices that have the Jelly Bean 4.2.2 update available.
Navigate to Settings > Apps, choose Google Settings Framework, and choose Force Stop. Select Clear Data, and open About Phone, then System Updates. Choose Refresh and the Jelly Bean 4.2 update should become available. On most devices as of 2015, Jelly Bean 4.2 is an obsolete update and isn't available, as Android released the update in 2012. The update is available on certain older devices, including the Galaxy Nexus, Nexus 7 and Nexus 10.