Not visible by default since Android 4.2. Do this to make it visible:
Go to Settings menu on your device.
Go to About submenu. In some devices the About submenu will be under “More”/”General” submenu. On some other devices (mostly HTC devices you will have to goto Settings> About> Software Information> More)
Now scroll to “Build Number” and tap it 7 times.
After tapping 7 times you will see an alert saying “You are now a developer”/”Developer mode has been enabled”.
Now if you go to your Settings menu, you will see the developer options submenu over there.
Tap on the Developer options and then turn on USB Debugging.
found here: http://www.technewscentral.co.uk/how-to-enable-usb-debugging-and-developer-options-in-android-4-2-and-higher-android-4-2android-4-3android-4-4/id_7250