Appeal deadline questions after an unemployment denial, office manager here

My claim was denied after 3 weeks of waiting, and the letter says I have a short window to appeal. Any experience at all would help. I have not done a hearing before and I am nervous. Did you bring documents or only talk?

Thanks for writing this out. I went through something close to it 7 months ago, and it settled down once I kept a simple log of every call and form.