Depends on the country. You will with this new mobile thingy also at least have to fill out the ROUTE/train-trip you intend to make. This will also help you when you encounter heavy delays.

NOTE that th travelplanner of EU/Inter is not always uptodate-esp. as since today about everywhere new timetables have come in force-and this also may apply to the need to REServe-or not. Always better to doublecheck the planner of the country/railway you want to use

You need to add the journey you'll make to your trip and then you need to add it to your pass, as with all journeys you make with your pass. After you've done that, there will be a QR code under “My Pass”.