For trains without reservations or with optional reservations, that QR code is all you need. It is your ticket.
For trains with mandatory reservations, you also need a reservation. Please take a look at this thread for ways to book reservations:
If you have any questions after that, then please mention route, date and departure time of any train you would like to book.
By the way, it is not a good idea to activate your pass, travel days or inbound/outbound journeys in advance. You never know what will happen and you can only cancel activation until midnight CET before validity starts. If something unexpected happens on your planned start day and you had already activated the pass, then it will be too late to change it. Therefore, only activate your pass on the start day, when you know your train is running and you are going to board it. Do the same with any new travel day (if you have a flexipass).
Yes, here it is also bonjour-6.40 in the morning and just getting light.
For les trains with NO RES yes, this is all you need to do. In the past: write it down on the special listings of the paper passes. That is enough for TER trains.
Now you are FR so know that this state-behemoth named SNCF wants anyone t RES in its prestigious TGV-all RES, also in other countries or for sleepers etc are totally separate from that code and need to be shown apart if asked for (often not at all). You can even keep that as paper print or as ticket from the counter in some cases.
ESpana is the very worst for needing RES, then comes of course this behemoth in the hexagone, together with its €* and Thalys
Just for clarification:
Every train you travel on during a travel day needs to be added to your trip and then transferred to your pass. This is then displayed in text below your daily QR code - this is similar to those with paper passes who need to write their train details in their paper diary.
Inspectors scan the QR code to check your pass is valid for that day and then the text to see that the train has been listed. In addition on trains with mandatory reservations they may also check that separately.