You need to buy a backplate for that. http://www.frozencpu.com/products/6553/bra-18/CPU_Fan_Retainer_Bracket_w_Backplate_-_AM2_AM2_AM3_FM1_.html?gclid=CPr0iK6gqr4CFcVffgod5bkA0Q
But, please, I have a10-5800k with a bunch of case fans and good air flow, but with the stock included heatsink I kept getting heat crashes 90 degrees +. The stock cooler is crap, I don't know why, but it's why tinier than the other retail amd cpus. Don't try to install it. My recomendation is just use the old fan; screw it on, or however it was already mounted. But if that gives you heat issues, buy that backplate and a hyper tx3 or some other cooler. Basically just try using the old cooler first. Remember thermal paste!