well the proper way to install it
get some isopropyl alcohol (cvs, walmart, etc.,) to clean off the bottom of the heatsink. on this image below, the south bridge has the "foxconn" heat sink. clean that off too.
install very small portion of thermal paste (best buy, radio shack, any PC store) on the heat sink and place it back on, locking the arms into place
if you really don't care, just place it back on and install the arms into place.