The main body includes the biggest amount of information. It is 80-90% of the whole text. There are no strict requirements, but you should not forget to use a logical sequence and correct wording. You can use the classic five-paragraph structure for your autobiographical essay if your ideas fit it. Anyway, you have to divide your writing into separated paragraphs to increase the readability of your essay. You should also create a logical connection between paragraphs. In this manner, readers will easily follow your thoughts.

Have you ever read an autobiography? Benjamin Franklin’s autobiography, for example, is an exceptionally powerful one. “DEAR SON: I have ever had pleasure in obtaining any little anecdotes of my ancestors.” That’s how it starts. But, Benjamin Franklin was an exceptional person, after all. That’s the point: autobiographies are for exceptional people. You’re exceptional, too. You have a special story that’s worth sharing. The only thing to learn is how to write a life story about yourself.
For example, if you grew up on a farm, you know the difference between the smell of hay and wheat, and certainly that of pig manure and cow manure—because you had to shovel one or all of these at some point. City people probably don’t even know there is a difference. Describing the subtle differences of each and comparing the scents to other scents can help the reader imagine the situation more clearly.
Once you have your initial list, elaborate on each key event in your outline. If you're using the autobiograa, fill in the blanks, and then write anything you remember about that point, a little or a lot, whatever springs to mind. Later, you might choose a single event that best illustrates each point in the outline and describe the event, using your theme statement to guide your description.
Develop a central theme, main idea or thesis that clearly explains the purpose behind your autobiography. For example, your theme might be about how you overcame obstacles to become a stronger person, or it might explain why a particular passion -- such as mountain climbing or rescuing animals -- is so important to you. Back your theme with details and background information about your life experiences. For example, you might explain that your dad is in the military, so you've had to learn how to adapt quickly to new schools and unfamiliar environments. Or, you might discuss what it was like growing up in a poor, single-parent home, but how your family was always willing to take in injured or stray pets.