cpu heat, fan, how?

i jsut bought an amd 6400 the fan it came with wont go in my dell dimension e521. so im using the hs the dell came with. but that doesnt have a fan it just has a hs that lays on top of it. the temps are around 43c on idle up to 49 on load. how can a make the fan go in. in the manual it shows a black squar mount for you to place it on. i dont have that.