The nightcrawlers found outdoors are not suitable for vermicomposting. Redworms are preferred for indoor composting. In the Denver area, you might look for them at garden centers and nurseries. Some bait shops also carry them. Redworms come to the surface to feed and then drag the food down into their bedding.
Worms can eat their weight in organic matter each day.
The box will yield some moisture so periodically drain the box to keep the worms from drowning. You can feed the worms kitchen scraps, such as apple peels and lettuce. Do not feed them dairy or meat products because these foods attract flies and cause unwanted odors. Worm castings should be removed once a month. Add scraps to only one side of the worm box.