In this picture from the mazda site you can actually see the hook points on the backs of the third row seats.
The net has to be folded and snapped to use it upright like this. I have also unfolded it and laid it over top of stuff with the seats folded down to keep stuff from sliding around.
I actually don't use mine that often. I thought I would. I wish there was a way to leave it hooked upright with the seats down but I haven't figured out a way. That way I could use it for smaller stuff while all the bigger sports equipment took up the rest of the space.