How do you remove the battery from the trunk? Where are the clamps?

see owners manual,on replacing battery.you need to replace with same type that came in it from factory,AGM type battery.it is vented to the outside of vehicle.also most years of the bmws,require to hook up batttery saver,before changing battery,to keep from losing preesets.also most newer years require that new battey is registered to your car,not sure about 2001.research and/or call dealer for more info.