Each DiscoverEU awarded traveller receives the link of his/her own booking form in the e-mail "Your #DiscoverEU booking form".
If you click on the booking form link in this e-mail, the login and password will be automatically filled. After logging in for the first time, you will be requested to update your password.
However, if you forget the password you have set, you can always reset it. To log in again, you will need to click on the "Reset your password" button on the login page. You will then receive an e-mail with one link to reset your password. (This link can only be used once.)