Pick a level location about 5 feet square, preferably out of direct sunlight and away from roof drainage. Then clear the ground of grass. Pile up the material directly on this spot, or put it in a composting bin or tumbler bought at your home center. You can also build a simple enclosure from chicken wire, scrap lumber, or cinder blocks. Make it about 3 feet square, and leave gaps in the sides to let air circulate.