I suggest you start with this thread:
There is no formula for writing an essay for any college. For the most selective schools, you will need to have excellent writing skills, but more importantly, your essay will need to show some qualities they value. It’s up to you to learn what qualities matter to those schools. As has been stated many times though, there is no guaranteed formula.
In general, some good advice is to write about something that matters to you, that shows who you are. Beyond that, do your research. The thread linked above is a good place to start.