Verla is often busy and not able to reply to all posts, so I wanted to make sure you got an answer.
Check out the illustration board lower down on this page, and the threads and links there can help you with some of the nuts and bolts of becoming an illustrator.
What is usual is that you, as an illustrator, would put together a portfolio and some other mailings, like postcards printed with your art samples, and send them to the art directors of different publishing houses. If they are interested in your work, they will then set you up with a project.
Try reading through this website and messageboard and see if your questions are already answered in other posts.