have to pull the pins out of the card. The things that are holding the heatsink on. Usually plastic . It works best for me just to pull the straight up rather than trying to break the back off. After that just clean and put as5 on then put new heatsink on. You have to use pins though to use as5 unless u engineer some other method. If the holes do not align with the heatsink u purchased you have to use thermal tape unless u think of another way.