you just show your paper pass, or mobile QR code ticket for that day. 

There is no difference in how you do if you have a reservation or if you don’t. The reservation is not a ticket so you always need to show a valid ticket together with the reservation.

If you have a mobile pass you need to add the trip to you pass and you wiĺl then get the QR code needed for the ticket inspection. If you can’t find the trip in the app you need to manually enter the trip to get the QR code.

If you have a paper pass you, as always, need to enter the trip in the Travel Diary and that is your ticket.

On STation generally you show nothing- except the very few countries which have gates or checks (mostly GB and ESpana for AVE-trenes. The checks are-if done at all- IN the trains.