Remove the following three screws securing the left fan to the logic board:

One 4.4 mm T5 Torx screw with 2 mm collar

One 5.0 mm T5 Torx screw with 2 mm collar

One 3.9 mm T5 Wide Head Torx screw

When reinstalling the fan and its screws, don't fully torque the screws until you've first installed all of them loosely, so that the fan can move a little and position itself properly as you insert the screws into their threaded standoffs.