If you have a few days set them on the countertop and allow them to ripen naturally. Do not put them in the refrigerator which will slow down the ripening process. You can also place them in a paper bag with a ripe apple, banana or avocado. Pears and these other specific fruits release ethylene gas which is a hormone that speeds up ripening. By putting them in a bag with other ethylene emitting fruits it traps the pears gas and adds more from the other fruit speeding up the ripening process.