To make an autobiography you should consider listing all the major events you've been through, then writing them down on a chronological timeline from your birth to the latest events of your life.
Before you even start decide if you life is really interesting enough for anyone to want to know about it - otherwise you could end up writing a very long and boring book. Jot down all the relevant dates in your lifetime - school achievements - job - family details. It is possible to make money from them. I helped my friend with his and he sold all his copies but you have to be realistic about the likelihood of this happening. Get someone who is completely unbiased to give you an opinion.