Got a denial letter for unemployment, what now? (update)

I got a denial letter last week saying I left my job voluntarily, but I was let go as a forklift operator. The letter lists a deadline and a hearing process, but it is hard to follow. Did you bring documents or only talk?

Thanks for writing this out. I went through something close to it 5 months ago, and it got easier once I kept a simple log of every call and form.