Summarize the following:
Because these worms don't lay eggs, you will need a few live adult microworms to start your culture. Remember that not all nematode species are a good food source, and some may even make your fish sick.  If your local fish store sells live food, check for microworms there. Try getting in touch with other local hobbyists through aquarist clubs. A member there may cultivate microworms and may be willing to either give or sell you a starter. For a few dollars, you can also order microworms online. They are sold everywhere from large general auction sites to small hobbyist forums. If the species is listed, check to make sure that it belongs to the Panagrellus genus. Panagrellus redivivus is the most commonly found microworm. Remember that microworms are tiny white worms that are barely visible to the naked eye. A started culture of a large group of worms should like a gray or light brown clump. If your starter looks significantly different from this, you may have another type of worm that has been misidentified. Almost any container can be used, as long as it's deep enough for you to fit your index finger inside. Clear containers with resealable lids are the most convenient. Some popular options include yoghurt tubs, mason jars, and resealable plastic food containers. Any type of human food-grade starch is usable. Common sources of starch include oatmeal, wheat flour, bread, cornmeal, mashed potatoes, and cereal.  If you're using a sealable container, be sure to poke small slits in the lid with a knife. Air exchange is necessary for a microworm colony to thrive. If your container doesn't have its own lid, cover the top up with tin foil. Microworms don't actually eat the starch. Instead, they eat microscopic yeast that feed on carbohydrates. You can find conveniently packaged dry yeast in the baking section of most supermarkets.  Some stores also sell fresh compressed yeast that must be refrigerated. If you bake bread or brew beer at home, you can also use the same yeast to culture microworms.

Summary:
Find a microworm starter culture. Buy or repurpose a container and some type of food starch. Obtain some active yeast.