Make sure that you insert the retention screws into the brackets before attaching them to the cooler base. If you never read manuals, bear in mind that these screws should go in counterclockwise.
After that put rubber rings onto these screws as they will protect the mainboard wiring against any possible physical damage during the cooler installation. The best would be to glue these rings to the mainboard PCB.
And now you can apply a thin layer of thermal compound to the CPU, turn the cooler upside down on the desk and then place the mainboard turned upside down on top of it. I advise you to install this massive cooler exactly like that and not as you would normally do (when the cooler goes on to the board). Now tighten the screw-nuts through the backplate:
This is when the bundled cross-cut screwdriver button comes in handy. The screws should be tightened evenly, in diagonal pairs. The hold-down pressure against the CPU is very high. Of course, you can also use plastic washers instead of a backplate, but in this case the heavy cooler will most likely bend the PCB a little.
Now all you need to do is install the mainboard with the cooler on it into the system case and attach the fan(s) to the heatsink:
Only when the whole thing is already inside you realize how massive it actually is. Of course, it is nothing like the gigantic Scythe Orochi, but still a very large cooler. And with two fans attached it turns even larger (~180mm wide):
As we found out later, with two fans installed for air intake and exhaust the cooler becomes the most efficient. If you have the fans direct the airflow towards the case rear panel, the CPU temperature under peak workload will be 2~3ºC higher than in case the cooler is installed as shown above.