Fill your growing tray uniformly with soil. If you are able to get hold of any manure, mix it with soil to form a compost. Being a fungus, mushrooms feed on decomposing matter such as manure.
Place the growing tray on top of a heating pad. The heating pad should have a temperature of around 70 degrees Fahrenheit.
Sprinkle the spores into the growing tray. Leave for three to four weeks, checking periodically to see if the spores germinate. They will look like thin white threads. When this happens, decrease the temperature of the heating pad to 60 degrees Fahrenheit.
Add 1 inch of damp soil over the spores and cover the tray with a damp cloth to maintain the temperature and moisture. Mushrooms should start to appear within eight to 10 weeks. You'll notice them when small white peaks begin to push through the second layer of soil.