Pull up one corner of the carpeting using pliers, then carefully pull up the rest of the carpet by hand along the wall closest to the wrinkled area. Go slowly so you don't fray or rip the carpet as you pull it from the tack strip.
Move along the wall using a power stretcher, stretching the carpet to ensure there are no wrinkles. Start with the length of the room, and reposition the stretcher every 18 inches. The power stretcher works by using the opposite wall as leverage, while you attach it to the carpet about 6 inches from the wall. Push down on the lever of the machine to grip and stretch the carpet until the wrinkles disappear and the carpet is tight. Before releasing the lever, push the carpeting back down on the tack strip.
Stretch the carpet in tight spaces where the power stretcher is too large to fit by using the knee kicker. Use the knee kicker as you would the power stretcher: Attach it to the carpet 6 inches from the wall, stretch the carpet, then push the carpet back onto the tack strip.
Trim excess carpeting along the baseboards using a carpet cutter or utility knife.