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.
Supporting Point Commuters appreciate the cost savings of taking public transportation rather than driving. Elaboration Less driving time means less maintenance expense, such as oil changes. Of course, less driving time means savings on gasoline as well. In many cases, these savings amount to more than the cost of riding public transportation. If you wish, include a summary sentence for each paragraph.