To see the option for USB debugging mode in Android 4.2 or higher, do the following:
Open up your device’s “Settings”. This can be done by pressing the Menu button while on your home screen and tapping “System settings”
Now scroll to the bottom and tap “About phone” or “About tablet”.
At the “About” screen, scroll to the bottom and tap on “Build number” seven times.
Make sure you tap seven times. If you see a “You are now a developer!” message pop up, then you know you have done it correctly.
Done! By tapping on “Build number” seven times, you have unlocked USB debugging mode on Android 4.2 and higher.
You can now enable/disable it whenever you desire by going to “Settings” -> “Developer Options” -> “Debugging” ->” USB debugging”.