Their specifications and measurements aren't detailed enough to find out how much shadecloth one would need. However I would estimate roughly (if the diagram is to-scale) 7' x 25' if you just wanted to cover 2 sides and the canopy. If you wanted to cover the backside, just add another 9' 6" x 11' piece.
Keep in mind I added 1 foot to all measurements, as I'm not sure the method you wanted to use to connect the shadecloth to the frame.