Pigmented leather also called protected leather is the easiest type of leather to clean. If the protection is still intact and has not been worn away be use and neglect.
You can put a few drops of water on the leather and see if it is absorbed readily or stays on the surface. That gives a clue about the level of protection present.
You did not mention the cause of the stain. If you don't know what the stain is, try to decide if it is water-borne or something oil based.
For a simple response to many water carried stains, use Strong Cleaner from LeatherMaster. Follow directions on the bottle. You'll put it on a sponge, work into a lather and work from the stained area outward until the entire cushion or other area is clean.
For oily stains, get the LeatherMaster aerosol degreaser. Easy to use. Shake can. Spray and use a sponge to work the foam into the leather. Let it dry and wipe off after it has dried. This may take a couple of applications depending upon the level of soil and how worn the leather is.