HiYou can't actually put it under the heatsink as that would interfer with the interface between the two. You will just have to attach it as close as possible and make sure it is firmly fixed.
I know you can control your fan speed by a setting in my bios under fan control. Or you can do the cool and quiet thing. Or try this http://www.newegg.com/Product/Product.aspx?Item=N82E16835220014 Its not expencive and it comes with a controler.