It's preferable to place these carpets outside the vehicle when you do so, but after a few times, you'll be able to determine just how much space you'll need to use to be able to find a place to put these. Pulling up the carpeting, will expose the cabinets that will later hold your seats. If there is a lever or pull-cord to fold these headrests down, pull it until the headrest have been completely folded down.  You may have to push the headrest into it's closing position. The lever is on the side of the seat. It should be just noticeable to the untrained eye. Doing this will expose an area that is able to accompany the seat. This should free the seats from their locked and upright position. It will also cause the seat to fall frontwards slightly. The seat should "roll over" onto it's back.

Summary:
Pull the carpet that is in front of the seat upwards with both of your hands, and place it to the side. Ensure that both headrests are down. Pull the lever that folds the middle seat's seat-back into a folded position. Take notice of the knob on the floor slightly underneath the seat. Push on the cabinet-door from the back, and hold it back. Pull backwards on the knob. Push on the back of the seat. Release the handle to the cabinet door you should be holding onto now, once the seat has been properly stowed into the basket. Repeat this process with the other seat, assuming you need the space to do both seats.Do the same with the other side seat, if you need to. Return the carpets to their normal positions over top of the cabinet door.