There are two pins sticking from your dash (instrument cluster) inder speedometer and under tachometer.
Set your OBC (button on turn signal lever) to display time.
Turn one or the pins, I think it is the right one, clockwise to advance time and CCW to retract it.
Push on the pin to switch between 24:00 and 12:00 format.
Al this should be in your Owners manual and Radio manulal.
If you do not have one, you can download it from www.bmw.com