Step 1: Turn the treadmill sideways, remove the four screws under the motor cover (left loose and right tight, use a Phillips screwdriver to remove the four screws counterclockwise respectively), then turn the treadmill back.
Step 2: Unplug the communication lines of the horn connected to the display, remove the four screws fixing the horn on the motor cover, fixing the new horn on the motor cover and plugging in the communication lines.
Step 3: Cover the motor cover, turn the treadmill over to lock the four screws of the motor cover, then turn the treadmill back