Open the doors (same way you usually do), and simply pull off from the outside inwards. They feel like they've snapped off, but they haven't! When you're finished, clip the doors on from the top clips first and then into the bottom clips.
Be careful not to let them try and close while you're popping them out or pushing them back in! Make sure the doors are open when you push them back in, otherwise they'll slide out half way through you clipping them back in.