Michael Schoch, Answers questions on Noodle
These learning materials on Noodle offer a variety of videos and articles that could be helpful in teaching your child about sleep.
Another great resource is this website entirely devoted to teaching young children about sleep.
Kids Health is an organization that also offers lessons and articles on topics related to sleep and children.
Hopefully these materials give you some ideas. If you'd like to research further, I recommend searching for books related to sleep on sites like Amazon or Goodreads.
Best of luck! Don't hesitate to ask more questions any time you need!