how do i turn off 'O/D-OFF' light on the Toyota Camry 2001 speedometer?

First, the "O/D OFF" light on your dash is telling you that it's already off. Second, there should be a button on your gear shifter (or maybe on the center console) that allows you to turn it on/off at the flip of a switch. People think of the overdrive as an "additional gear". Although it's not exactly correct, this "additional gear" allows for fuel savings during long (highway) drives. You should try it sometime. You could turn it on and should notice a fuel savings across the span of your trip.

what about, if the O/D went light off...so mean light bulb out too right?

I just turned my overdrive light to back off and it was on the handle the shift gears. Thank you so much!

You are the best!, the picture really told me how to find it. Other spots on the website did not point to it like THIS did!

Thank you so much for the picture. It was very useful and I would have felt foolish taking it to a mechanic and being charged a bundle to push a button.