The Italo website says to print your tickets for the train once purchased. We went back and forth between Rome and Naples. We had printed tickets the first time (two on one printout), and e-tickets on the phone the second time. Both worked. Having a printed ticket is not a requirement as long as you can show the QR code on your phone.
We used the cheapest SMART fare... it went very well. Smooth, quiet, comfortable and fast. Baggage storage above the seats, behind the last row of seats, in other random places and in a baggage storage area just inside the entry door to each car at one end. It was about 1:12 duration at speeds around 180mph! Frequent, reasonably priced and highly recommend. Don't forget to know the last stop on the route you are one. Going, it was Naples, our destination. Coming back, it was Trieste, even though we bought Napoli (Naples) to Roma (Rome). At that time there was no mention of Trieste. But the board in the station showed Trieste, not Rome. Have fun and don't be afraid to use the trains. We had too many bags that were too heavy. That made it a challenge, but still doable. Take Rick's advice - go light and small! We tried, but we had a boat trip in the middle that made it difficult. But, we learned our lesson.
Trains and planes are in a transition stage where some folks have paper and some have screens. Eventually they will want you to use only phone screens.
A recent informal survey at an airport lounge in Denver showed most people using screens, with a few oldtimers like me showing paper. Which has a bar/QR code so it's effectively a paper screen.
Glad you had good luck. So much easier to use the train app, isn’t it?!
I downloaded Trenord app, the regional train company for Lombardy for my train trip today, buying the ticket before I left my hotel this AM. So easy!
I also screenshot the route so I’d have the reference.