Carefully route the motor wires as shown in the figure.

Verify that the wires sit correctly in the channel.

This surface will be touching the extruder_body. It is the side with the manufacturers label on it. The wires come out from this side and the fan should be oriented so that they point towards the rear of the extruder.

Carefully route the hotend fan wires in the channel of the x_carriage.

Attach the hotend fan with four screws. Follow the screw type according to your hotend fan:

Sunon & Delta : M3x16 button head screws

Noctua : M3x14 socket head screws

Check that no wires are pinched. Check the orientation of the hotend fan, the air should be blowing over the hotend heatsink. On the edge of the fan body, there are usually two arrows, indicating the direction of rotation and direction of flow. Ensure that the arrow indicating flow is pointing in towards the hotend.