Using a PH#00 screwdriver unfasten the eight not-releasable screws that secure the heatsink to the motherboard. Nearby the screws you will notice that numbers have been impressed: the screw marked in red is the first one that has to be unfastened, follow then the order.

Once you are done with the screws, grab the heatsink and the fan as it is shown in pic#2, tilt them up a bit, and carefully slide them forward a little: until the fan is free of the left display hinge marked in green in pic#1. Finally then, rise them up and put them aside.