To use a promotional code, you need to start a booking process.
After entering your travel details (1) in the simulation module on the homepage, click on "Get my fare" (2) and "Book".
Once on the booking page, you will find a "Promotional Code" field (3) on the right side of your screen where you can enter your code. Remember to click "enter" on your keyboard
If the code is valid, the field will turn green and your discount will immediately be reflected in the summary on the right of your computer screen.