1) Ensure that the handbrake is up.
2) Put the gear lever into neutral.
3) Press the clutch pedal fully down, without pressing the accelerator.
4) Turn the ignition key to AVV and let it go the moment the engine starts.
If the engine does not start at the first attempt, return the ignition key to STOP before trying to start the engine again.
If the warning lights 
stay on when
the ignition key is at MAR, turn the key to STOP and then to MAR again; if the warning
light stays on, try with the other keys provided.
If you are still unable to start the engine, perform the emergency start-up procedure (see section “In an emergency”) and go to a Fiat Dealership.
IMPORTANT
Never leave the ignition key at MAR when the engine is off.
See also:
22. Electronic Stability Control (ESC) Activation /Malfunction Indicator Light
The ESC Activation/Malfunction Indicator Light in the instrument cluster will
come on for four seconds when the ignition switch is turned to the ON/RUN position.
If the ESC Activation/Malfunctio ...
Key without remote control
Key (A) (or (C) in alternative), delivered in two copies when the car is not
fitted with remote control, controls the following:
❒ the ignition switch;
❒ the door and boot locks;
...
Lower vents
(C) - (D) Fixed vents for conveying air to the footwell. ...