Open a 6-foot stepladder and place it under the open garage door.
Locate the red release knob on the garage door trolley, which is the part that attaches to the track mounted to the garage ceiling.
Pull down on the release knob to disconnect the door from the track.
Remove the ladder if the garage door stayed fully open. Use a helper to assist you in lowering the garage door if it fell against the top of the stepladder when the release knob was pulled. Note: If this happened, the door springs may be weak, and the door may be too heavy for one person to lower.
Close the garage door by hand using the handles on the door.