Thanks to this earlier question on the SNCF Voyageur program, I now know roughly how the program works, and I've signed up for it. Despite some issues with previously bought tickets, I've managed to credit some TGV journeys to the program.
On logging into my account today, I notice that there seems to be a discount available for me to use:
It looks like I have a €5 discount available to use in the next few days before it expires. (Sadly I didn't notice it before). However, I can't for the life of me work out where to enter the code when booking a TGV ticket to take advantage of the discount.
So, does anyone know how/where you go about booking a discounted ticket using a "code avantage" shown in your SNCF Voyageur account?