If it's the butt part, just grab the front part of the seat (where your knees are when you sit down) and pull upward, there's 4 semi spring locked clips on the bottom of that piece of foam.
This was on a 98 B5, i don't know if anythings changed in the newer models.. but I highly doubt it.
If you're talking about the fold down backrests, then you have to fold both of them down, then look between the 60/40 split and you'll see a Torx screw on a little bracket. Undo that, and simply lift the corner of the seat up from there. You have to slide the seat a few centimetres towards the inside of the car to clear the pins on the outside sides of the seats.
ACraig