Indicator Bulb replacement
First you need to get to it in my 1.2 I can get to them from above however Fiat have kindly given you an access hatch in the arch liner
you need to locate the little cap which holds the Indicator bulb this opens with an anticlockwise twist of about 1/8th of a turn (it is tight due to the O-ring seal) then a pull
this releases the bulb in the holder
To remove the bulb from the holder push down on it and turn anticlockwise and it will pop up
replace and reinsert reversing the above method (NOTE the cap will only close in one position so don't force it)