Knowing how to write an essay about yourself can be a straight up autobiography or an anecdote related to a certain theme. If you need an autobiography, it is likely that your paper will be written on a formal tone depending on your level--as all essays have varied quality, e.g. High School or College level. If it is an anecdote, of course, feel free to be creative, but be crystal clear. But, it should not be difficult. You are writing about yourself, which means that you know the subject more than anyone else.
It is relevant to note here that biography is different from autobiography. Although both are write-ups regarding a life of a person, the difference is on who the author is. If you are writing the life of a friend, it is called ‘biography’. On the other hand, when you are writing about yourself, it then becomes ‘autobiography’. As noted, this task should be easy because you know the details of your life more than anyone else – your full name, your birth date and place, your parents, your siblings, and everything else. For a start, you can mention these details as your introduction, but try not to use the cliché: “A wonderful baby was born to Jane Doe and John Doe on a cold evening in San Francisco.” Believe it or not, your teacher read that line a thousand times already. From there, you can work your way around to narrating your story, however, try to insert life lessons applicable to your story. Also, feel free to share advice on certain events which you have experienced. Do not make your autobiography a personal data sheet in essay form as this will discourage your readers to continue reading. Instead, make them think. Make them analyze your story, make them agree or disagree with your advice. Make them want to read more. Hard facts about you are not the best pieces of information you would like to add to this creative piece, save that for professional purposes.
Knowing how to write an essay about yourself does not mean that it has to be an autobiography. An anecdote is a narrative of a real incident, occasionally written in a humorous way, but definitely connected to an important message. So, if you are not required to write an autobiography, an anecdote is a perfect alternative. All you have to do is recall an important piece of knowledge, realization, a life lesson, or anything that had a great impact on you, then narrate the back story of that knowledge in any way you want to. You can use metaphors or any literary device you deem appropriate to your essay to evoke sympathy and rapport with your readers. You do not even have to reveal that it is you who you are writing about until the end of your story. You can also find a memory which you can relate to a current social issue. Whatever it is, always remember that you are writing your own story. Knowledge of how to write an essay about yourself also gives you a chance to connect with your family, browse through old photographs, and discover the funny and embarrassing things you used to do when you were a kid. On top of that, you get the chance to spend time with them amid all your school works. Whatever you write about in whatever way you want, keep in mind that that essay is about you, and written by you. Take it as a little "me time", and nothing could go wrong with that.