You need a user name and password and your VIN number (the number you can see through main screen near passenger side).
This sets up an account for you that registers your vehicle and tells you when next service due, next mot, etc etc. You can order spares / accessoires and memorabilia - I've just bought a Citroen T shirt, a DS4 model, and a key ring (don't ask!). You can also order map updates etc and register for any recall / fault updates.
I know its a gimmick, but it may be useful for people to monitor and maintain their car better.