This topic is misleading, as after I posted my original message, I figured out how to install the backplate onto the motherboard. Now that I've done that, I have another problem. This massive piece of metal is held on to the motherboard with a single screw. Mounting it involves mating it with a clip on one side of the mounting bracket, then securing the other side with a single screw. This arrangement won't support its own weight. As soon as I got the cooler installed and turned the case upright, the mounting bracket let go and the cooler was hanging by a thread. This is either the mother of all bad designs, or there is something crucial missing from the instructions.