Guide all wires along their respective little trenches, to ensure no wires get pinched when the backplate is reassembled.

Insert the fan in its slot, while keeping the wires that go behind the fan down.

Pay attention to the direction of the fan. If mounted incorrectly, the fan will be blowing air out of the box instead of into the box. The blades of the fan should be curved upwards from the center outward.

Guide the remaining wire of the fan along its little trench, with the rest of the wires.