Raise door completely and disconnect power and the lifting arm of garage door opener.
Retain door by fastening “C” clamps under bottom rollers on each side. With tension completely off of cable, untie loose end of cable from track support or from the attaching plate.
Thread the cable through the pulley, unhook cable loop from bottom bracket.
Dispose of cable.
Hook cable loop of new cable onto the bottom bracket.
Re-thread the cable through the pulley and retie loose end of cable from track support or the attaching plate.
Slowly lower the door by hand to check that the cable is properly fed through pulleys.