Carefully peel the two foam pieces stuck over both the heatsink and the fan away from the fan.

The foam only needs to be peeled back enough to clear the fan.

The foam is really delicate and tears easily. Use the following technique to peel the foam:

Insert the point of a spudger underneath the part of the foam that isn't stuck against anything,

Press the top of the foam with your finger to hold it in place.

Roll the spudger tip underneath the foam all the way to the other end of the foam to release it.