Installation of the Kühler 620 is relatively easy, that is if you can understand the frustratingly inadequate instructions or figure out how it all comes together by looking at the various parts. The first step is preparing and mounting the back plate, which requires the use of the four provided washers which are not mentioned in the instructions. They act as spacers fitting over the threaded inserts (seen on the four corners) between the back plate and the motherboard, and without them the cooler will not be held tightly against the CPU. The threaded inserts fit into one of three slots on each corner depending upon the chipset, and a specific combination will give you the proper alignment needed.
With the back plate in place, the pump mounting bracket is assembled using the appropriate retaining ring, thumb screws and snap ring. Unfortunately the instructions for this step are mysteriously absent,though it's not particularly hard to figure out. I removed the pre-applied cooling paste and smeared some Arctic MX-4 for consistent testing with other coolers in our test beds. Mounting the pump on to the CPU was quite easy, which left me with the decision of what configuration I wanted for the radiator-fan assembly.
Following the instructions will put the fan in a position such that it will pull air across the radiator and exhaust it out of the case. This is done by taking the longer set of screws (see fastener picture above) and fishing them through the case and the fan, then threading them into the radiator. The two sets of short screws included with the cooler are unmentioned in the instructions, but those with a keen eye (not me, though) are quick to realize that they're there to allow for a push configuration. Using your favorite set of four of the included shorter screws, attach the radiator to the back of the case and then attach the fan to the radiator with the long screws. There isn't a discernible performance difference between the two arrangements, so go ahead and pick whichever one you like. As you can see in the pictures, the push arrangement routes the hoses toward the top of the case which keeps things a little tidier.