The procedure for installing the Tower 120 Extreme is fairly straightforward but there are a few niggles. Because it uses effectively the same mounting bracket as the Alpenföhn Nordwand, there isn't much to elaborate on top of that but I might as well give you a quick rundown seeing as how Tuniq have put in the effort to create a clear manual individually detailing installation instructions for each socket type.

LGA 1366
1.First insert the four screws (T120-08) through the back of the back plate and secure them using the screw caps (T120-06). The hole have grooves to ensure that the screws go in the right way and lock.
2.Insert the washers(T120-09) onto the screws on top of the screw caps.
3.Install the back plate onto the motherboard.
4.Squeeze 0.1ml of the TX-3 thermal on the surface of the CPU.
5.Install the cooler onto the motherboard after removing the protective film and secure it using the provided spring screws (T120-04). Screw them on diagonally and gradually.

LGA775
Installation for LGA775 is exactly the same as LGA1366 except for making sure that the screws go in the appropriately labelled holes in the back plate.

AMD AM3/AM2(+)
The difference with AMD sockets is that the stock cooler support has to be first removed from the motherboard and instead of the Intel screw caps and washers, use the AMD ones (T120-07 & T120-10). The T120-03 fittings also have to be screwed onto the cooler's pre-installed bracket using the T120-05 screws.

The main problem with installation is the final step when placing the cooler onto the motherboard/ back plate fittings. The sheer size of the tower overhangs the screws rendering it nearly inaccessible. Unless you're a contortionist or have baby hands, this bit might take a while. Alternatively make sure you install the cooler before placing the motherboard back into your case!

I'm sure you've had enough of my ramblings so on to the results.