Activating USB Debugging option is little different in Android 4.2 Jelly Bean than what we used to see in earlier version. If you recently updated your Nexus device with official Android 4.2 Jelly Bean OTA release then you probably already noticed that there is no USB Debugging option under settings as Developer Options no longer there.
Without USB Debugging option enable you can’t control your PC via ADB. ADB access is required to do several development tasks via ADB commands.
So, how you going to active USB Debugging on Android 4.2 Jelly Bean
Step 1: Go to Settings > About phone.
Step 2: Now tap on Build Number seven times repeatedly. Once you press it 5 times it gives you a quick note: “Press it two more times to be a developer!”. And, after tapping 7 times you will see ‘You are now a developer’ message.
That’s it! You can now see Developer options under your setting. Follow this guide to activate USB Debugging now.