It's in the manual. Driver section,starting, Back-up method of starting, page273.
"Back-up method of starting: Your IA key uses a radio frequency signal
to communicate with your vehicle and authorize your vehicle to start
when you press the START/STOP button and apply the brake pedal. If
excessive radio frequency interference is present in the area, or if the
battery in your IA key is low, it may be necessary to start your car by
inserting the IA key in the back-up slot, located at the front of the center
console storage compartment. Insert the IA key into the slot with
buttons facing out and with key ring up. After inserting the IA key into
the back-up slot, use the START/STOP button and brake pedal to start
your vehicle as usual. The vehicle should respond normally as long as the
IA key is in the back-up slot. Once the vehicle is started, the IA key can
be removed from the back-up slot, if desired."
It doesn't say what to do if IA Key is dead! Call wife I guess. Would hate to be in that situation. I can hear her now. LOL