The topic you have chosen must now be explained, described, or argued. Each main idea that you wrote down in your diagram or write a three paragraph essay will become one of the body paragraphs.
If you had three or four main ideas, you will have three or four body paragraphs. Each body paragraph will have the same basic structure. Start by writing down one of your main ideas, in sentence form. Next, write down each of your supporting points for that main idea, but leave four or five lines in between each point. In the space under each point, write down some elaboration for that point. Elaboration can be further description or explanation or discussion.