Remove the creased cushion or backrest pillow from your upholstery, if possible.
Set the item on the floor of your bathroom, upright, and run the shower until a full steam develops.
Let the item set in the steamy room, with the door closed, for 20 to 30 minutes. The steam should loosen the crease.
Wipe the moisture from the upholstery with a clean, lint-free cloth.
Set your iron to "Warm," and let it warm up for about 5 minutes.
Cover the crease with a large cotton or linen cloth. An old pillowcase is perfect for this job.
Run the iron over the cloth, concentrating on the area positioned over the crease, for 1 to 2 minutes. Keep the iron moving, so as not to burn the leather.
Lift the cotton cloth and inspect the crease. Repeat the ironing process, if necessary.