Appeal deadline questions after an unemployment denial (Boise)

I got a denial letter last week saying I left my job voluntarily, but I was let go as an accountant. 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?

Stay calm and stick to facts. Mine lasted about thirty minutes and felt more like a conversation than a trial.