What John said. But first I would take the loco apart, remove the motor, and see if the wheels / drive rods will rotate freely. A needlepoint oiler will help you get oil to the bearings where the axles meet the chassis.
Some of these early 2-6-0s were "sidewinders" with a small motor mounted transversely in the chassis. On those you can probably turn the wheels with the motor connected. Some pics might be helpful here.