How do I turn on vibration for my iPhone ?
Setting/Sound ~ Vibrate ON/Off
There are three buttons to the left of the unit when you hold it facing you. If you flip the top switch down (push it against the back of the unit), it will turn off the ringer and go into vibrate mode.
Alternatively, you can also make the phone vibrate and ring. That is accomplished by going into Settings, then Sounds. If you look down several options, you'll see one that says Vibrate (not the one listed under the Silent heading). Enabling this will add vibrate alongside the ringer.