When I begin to research a topic, I often start with children's magazines and books. I can get a basic understanding, especially if I am not an expert on the topic. The fact that an article for children is short does not mean less vigorous research. Magazine guidelines will tell you what the policy is. If a query is required, send a one-page letter describing your idea in the style that you will write the article.
Some magazines also like to see a sources list.
If they want the entire article, you are ready to write. For step eight, you are finally writing. Remember to use vivid words, punchy sentences, and child-appropriate examples. To state the length of a dinosaur, tell how many school-buses that is. To place the time of a person's life, say it was in the time of your grandparents, or when our country was beginning.