Autobiography help please....?

I know that its supposed to be about myself and no one in the world really knows about my life but me but i just need a little help on getting started and what to really talk about. i havnt been to school in years but now im doing this online schooling and they are asking me to do this autobiography. Can anyone give me any suggestings? Please mature answers only....no time for games on here...thanx for any help i receive