The Masterair cooler you're referring to should come with mounting hardware for the 115x sockets.... unless they forgot the mounting hardware for the other sockets. The other exception is if you bought the Cooler off the 2nd hand market and the seller lost the mounting hardware for the other sockets.
Typically socket 2066/2011-v3/2011 motherboards come with a backplate and standoffs that are preinstalled. Socket 775, 1366, and 115x will need a backplate. So the mounting screws and parts for Socket 2066/2011 will be different than what used with other sockets.
-With many CPU coolers, the mounting system uses a lot of small parts. So you really need to read the instruction manual carefully and organize the parts you will need.
-If you don't have all the parts you need, you can contact Cooler Master and they might sell you the proper mounting hardware. You can also buy additional mounting hardware at ebay. If you bought this CPU cooler brand new at amazon and you didn't get the proper hardware, then simply return the item.
*Socket 1156, 1155, 1150, and 1151 use the same mounting pattern.
*For what it's worth, the Masterair 620 and 621 are not very good coolers when compared to other coolers in the same price range. The Scythe Fuma, Scythe Mugen, and Thermalright Macho Rev.C are much better alternatives.