There are 2 pressure clamps underneath that just press on and can be pulled right off. Basically pull straight down on the panel and it comes off.

Use this link. On the bottom of the Bosch page is link for vehicle specific instructions. It is the same as changing the air filter for the air conditioner. There is a good illustration of where the clips are located.

http://aa.bosch.de/advastaboschaa/Product.jsp?prod_id=91&ccat_id=37&language=en-GB&publication=1&flash=false