remove the screws off the front side of the plastic pieces
the rear section of that plastic piece is held on by plastic pins in rubber grommets. kinda angle the filler piece doen and pull it out. dont scratch anything. the lip on that plastic piece is held on by the seat. heres what it looks like underneath, you can see the grommet if you know where its at.
once the plastic pieces are off youll see 2 10mm bolts on each side of the seat. remove them and lift up on the seat and there you go.