Appeal deadline questions after an unemployment denial - 6 months and counting

My claim was denied after 13 weeks of waiting, and the letter says I have a short window to appeal. I have read a lot of threads here and could not find my exact situation. 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?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.