If its the saloon model you will have to remove the seats first as the top edge of the rear seat overlaps the parcel shelf.
The bottom part of the seat will need to be removed first, there are two red coloured tabs to release the seat base. I'm not sure how to remove the seat back but I expect it will be obvious once the bottom part has been removed.
You may also need to unclip some of the tabs from inside the boot underneath the shelf.
You remove the seat back by undoing some screws at the base of seat back-you will see the screws after you remove the seat base. The seat back is then removed in an upwards direction as it hooks into slots near the top. You may also have to remove the C pillar trims-held on with 3 clips at the leading edge nearest the back door and one at the rear and then pull forwards. Some U shaped edging strips may need to be taken off also.