Place a piece of lumber --- a 2-inch by 4-inch board --- against the baseboard opposite the area with the crease in it. This protects the surface.
Set the power stretcher at the baseboard on the wall opposite the crease. Start opposite the middle of the crease, and work to the left and then to the right of the center of the crease for the best results. Using the power stretcher a few times may be necessary, depending on the size of the crease.
Add extensions to the power stretcher until it is approximately 6 inches from the other wall.
Push down on the lever, but don't release it yet. This enables the teeth to grip the carpet.
Adjust the carpet in front of the head by attaching it to the tack strip that extends out from the area. Release the lever, causing the power stretcher to smooth and flatten the crease. Repeat this step in the surrounding areas if parts of the crease remain.