If you would like your child to work as a professional actor in television, film and stage, then you will first need to get a talent agent for your child. Talent agents promote their clients to casting directors and producers, and negotiate contracts for their clients.
Make sure that you and your child can be available for auditions. For professional work, you will need to be in or near a large metropolitan area. Los Angeles and New York are the primary centers for working actors, but children can also find work in Chicago, Dallas, Orlando, etc.
Help your child learn about acting by enrolling him in a good acting class. As a beginning actor, he should also be trying out for local plays and school productions.
Work with your child's agent to create excellent promotional materials for her. Your child will need professional headshots (8 X 10 photographs) and a resume.
Make sure that your child is set to legally work in your state. In California, for example, children under 19 need an entertainment work permit and a special trust account in order to work in movies and television.
Make sure that your child is fully prepared for every audition that the agent obtains for her. You may need to hire an acting coach to help her fully prepare!