To turn on USB Debugging, begin by pressing the Home button to return to the main Android home screen.
Click the Menu button on your device to bring up the pop-up menu. Tap on the Settings button.
Scroll down the Settings list until you come to Applications. Tap on the Applications header.
In the next screen, select Development from the list.
In this last screen you will see the option to turn on USB debugging. Check the box to turn it on or off.