I assume that, unlike nearly all of the 'Merican Vits, yours has a manual gearbox. (lazy, effin' Yanks... Wait, that would describe me!

)
If it IS an automatic, the switch, most likely, is inside the center console in the area next to the shifter lever itself.
In this situation, the switch is mechanically activated by the movement of the shift lever into the "R" position.
Otherwise, the reverse switch for the manual gearbox is located on top of the gearbox case just forward of the shift tower. it is activated by reverse linkage inside the gearbox.
And I also do not know which switch is which (say that fast five times!) - the emissions switch or the reverse light switch...
I hope that this helps!