Agree with usualhopeful. This should be mentioned by your GC. And yes, you can write your essay about it, but it needs to be specific. Just saying yiu were homeless doesn’t give colleges an insight into,who you are as a person. Be specific, relate it to an incident, or a particular lesson learned, or how you coped and how,it made you stronger. The essay is a way for colleges to learn something about you that can’t be learned from the application. They want to admit people they like.