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

My claim was denied after 18 weeks of waiting, and the letter says I have a short window to appeal. I worked as a data-entry clerk before this. The letter lists a deadline and a hearing process, but it is hard to follow. If you have appealed before, what helped you prepare?

I printed my emails in order and wrote a one-page timeline. The hearing officer kept going back to it.