Got a denial letter for unemployment, what now?

My claim was denied after 17 weeks of waiting, and the letter says I have a short window to appeal. I do not usually post, so bear with me. 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.