not sure if your layout is the same as i have a 3.0l a4
remove airduct and airbox cover, these simply lift out, the airbox is now exposed, its then simply a case of undoing 2 philips head screws on the top corners of the box,when these are totally undone the box will be able to open enough to pull out the old filter, give the duct a quick clean of leaves dust etc,then slip in your new filter, screw box back up and clip ducting and cover back in place
job done