Pull back the carpet and pad from one of the room's corners, about 2 to 3 feet down both walls. The corner to select is based on which direction you will be stretching your carpet. Choose a corner across from the bulge so that when you stretch the carpet toward the corner, the carpet will flatten. Pull each staple out of the carpet pad using pliers.
Set up an automatic carpet stretcher on the floor, against the wall across from the corner where you loosened the carpet. Use the carpet stretcher's extension tubes to extend the stretcher's other end straight across the room, stopping approximately 6 inches from the opposite wall.
Push down on the carpet stretcher's handle to pull the carpet toward the wall and flatten the bulge and ridges in the carpet. Only pull the carpet until the ridges are gone. Overstretching a carpet will result in tears.
Angle the carpet stretcher toward the loose corner, and stretch the carpet toward the corner. If your carpet has many bulges and ridges, it will be necessary to loosen two corners, one next to the other. Move the carpet stretcher along the opposite wall every 18 inches, pulling the carpet toward the loose corners until all ridges have been removed.
Place a knee kicker on the carpet near the loose corner, about 3 inches from the wall. Hit the knee kicker with your knee to push the carpet toward the wall, and hook it over the tack strip. Move the knee kicker down about 6 inches and repeat. Continue until you have reattached the loose corner to the tack strips.
Use a carpet tool to stuff the carpet between the tack strip and the wall. Cut the extra carpet off using a carpet cutter.