Make sure there is no fire in the fireplace and that the interior and surrounding areas cooled completely. Remove any logs, grates or other items from the interior of your fireplace. Cover your carpet and other surfaces with protective tarps.
Look up into the chimney with a flashlight and find the damper. Examine the damper lid. Determine whether the lid is attached to the flue with bolts or whether it is a lock type with a gasket seal.
Remove the bolts from your damper with an adjustable wrench. Lift the lid away. Follow the manufacturer's instructions for removing your particular lid if it is a lock type.