Place one lump of dung in a jar with a loose fitting cover so that it gets plenty of air. The loose lid holds in moisture, yet admits enough air for the desired aerobic conditions. Fungi must have oxygen. Furthermore, air prevents the growth of anaerobic bacteria which produce the foul odors associated with rotting manure. Actually, this project is going to be free of strong odors if you are careful to avoid getting the dung soaking wet.
Fungi require moist conditions for growth.
The ball of dung should be in contact with liquid water 2 to 5 millimeters deep. Add water as needed to maintain a dryish surface, but moist inside the dung ball. Room temperature is ideal. If in doubt start several jars and keep them in different locations. A succession of fungus species will appear.