Denied unemployment, how do I appeal? - 15 weeks in

I got a denial letter last week saying I left my job voluntarily, but I was let go as an accountant. I am in Portland, in case local advice matters. My employer's version of events does not match mine, and I have emails that show it. If you have appealed before, what helped you prepare?

Legal aid offices and some workforce centres help with unemployment hearings at no cost. A call is worth it.

Thanks for writing this out. I went through something close to it last year, and it got easier once I kept a simple log of every call and form.