Gently pull on the heatsink to remove the heatsink from the graphics card.

Do not pull it too hard, as you will need to remove the cable from the heat sink's fan to separate the two pieces completely.

Next to where the 6-pin power connector is, is the fan connector. Handling the heat sink's fan cable from the sides, gently remove the cable from the slot.

If you pull the fan cable from the cable itself, you will likely destroy the fan cable.

When reassembling, do not make any adjustments when seating the cooler to the PCB, as this can affect the seal of the thermal paste, and reduce its effectiveness.