You press CAR + SETUP at exactly the same time and hold for a few seconds until a green hidden menu appears. It is all in techno-cryptic German, but is rather different from the Range Rovers in that it can be used to enable various options, some require additional hardware such as TPMS and oil level, others (such as adjustable ambient lighting) don't.
http://www.youtube.com/watch?v=q857HmEvu3o