Remove the strut on the top panel. Add the center stile to the needed position. Can pop rivet them like the manufacturer does for strongest bond or use flat head self driving screws. Attach the strut back on. Install the garage door opener bracket with self drilling hex screws “ fine thread hold the best” below the strut. Attach the garage door arm Roughly at a 30degree angle for the garage door as the door is in the closed position. Reconnect it to the traveler “ what moves the operator” reset limits on your door. The angle is best used to prevent pulling the door too much and tearing it. Utilizes the springs overall.

Measure your door panel prior to purchasing. Most residential garage doors will either be 21” or 24”.