If you have a passion for writing books for children, and strong writing skills, chances are you've already given thought to writing children's books and submitting them.
The best way to get started is by spending some time in your local bookstore and library, and get a feel for what the current bestsellers have in common.
You can take writing courses and read some good books in order to really hone your writing ability.
Decide what type of children's book you want to write, such as poetry, folktale, picture books for very young children, historical fiction, biographies, mysteries, fantasy, adventure, non-fiction, etc.
You'll need to do some digging online for information about where to send your manuscript once you've completed it. There are many resources, writer's groups, websites, and books, to help you along.