Adding fog lights to the 453 is a 3 part situation. You have to:

1 - Fit the fog lights and the wiring loom.
2 - Code the fog light ability.
3 - Fit the replacement stalk.

Step 1 - Fit The Fog Lights And Wiring Loom

Remove the front bumper.



Use a Torx25 bit to remove the screw holding in the fog light blanking plate.



You'll need replacement panels from a smart dealer. On the fortwo, the smart part number is:
A453 826 06 00 - This will get you a pair. 1x left, 1x right. These were only £13 for the pair when I bought them.



On the forfour 453, the parts are different so the part numbers are different. Forfour = A 453 826 10 00



You have an option. Standard halogen fog light units or LED fog light units. More on these later.