If you have FIP coupons, then you're in the wrong place here. The department that provided you with these coupons, should be able to say what kind of reservation you need.

In addition, you can use the extensive FIP documentation of the British RDG:

https://www.raildeliverygroup.com/rst/where-can-i-go.html#Europe

In particular the "Travel tips for Europe”. Look under Italy what kind of reservation you need.

@Eric69  there is a Facebook group called European Staff Travel there are many FIP Experts that can provide you more detailed informations.

I´ve booked my reservations always directly in Italy at the Ticket desks and noticed that the Cupons in Italy are for the Highspeedtrains almost worthless I paid 10€ for the reservation (finally it was a Interrail/Eurail Reservation even with a Fip Cupon but offical its a different one with a own limit) and a colleague just paid with the FIP Discount Card 15€:D

With a FIP coupon in Italy, you pay the difference between the regional full fare and the long distance full fare (only available in Italy at the ticket office). For an intercity, that is usually quite affordable but for a Frecciarossa, that may still be quite expensive, depending on what public fare is available. Frecciargento is somewhere in between.