As you will receive your bracelet at the festival venue, you will only be able to link it from then on. The action in the app becomes available a day or 2 before the start of the festival (Graspop Metal Meeting, Rock Werchter, Suikerrock). You enter the code on the back (6 digits/letters) when you get your bracelet on the festival grounds, and you're all ready to grab a free consumption right away!