Its best to ask Fiat and it should be in the owner's manual.
If it has the manual type gearbox with the selespeed type automatic gear shifting, it should be parked in 1st gear**. When you switch on the ignition it will ding annoyingly at you to select neutral.
The E button makes it shift up sooner to save fuel.
** Seemed odd to me but that's what my Mother's 2007 Panda users manual says.
I think its a great system. My only gripe is gear lever works back to front. Forward for up and back for down is so not intuitive.