I too would like to know this. I have the rear defroster, it works.....I just don't know how. I 'spose I need to get the FSM ordered.
The manual says that your mirrors come on with the rear widow defrost switch.
Maybe just found the answer for both of us. The lower right button on the climate control area is the rear window heater. It is the rectangle box with three squiggly lines. SNOKING
Heated Mirrors — If Equipped
These mirrors are heated to melt frost or ice. This
feature can be activated whenever you turn on the
rear window defroster (if equipped). Some vehicles may
not be equipped with rear window defroster, in this case
the heated mirrors will still function as intended. Refer to
“Rear Window Features” in “Understanding The Features
Of Your Vehicle” for further information.
REAR WINDOW FEATURES
Rear Window Defroster
The rear window defroster button is located on
the climate control panel. Press this button to turn
on the rear window defroster and the heated outside
mirrors (if equipped). An indicator in the button will
illuminate when the rear window defroster is on. The
rear window defroster automatically turns off after approximately
10 minutes. For an additional five minutes of
operation, press the button a second time.
NOTE: To prevent excessive battery drain, use the rear
window defroster only when the engine is operating.