Denied unemployment, how do I appeal?

My claim was denied after 26 weeks of waiting, and the letter says I have a short window to appeal. This is my first time dealing with any of this. 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?

File the appeal before the deadline, even if you are unsure. You can gather documents afterwards. That is the one part I would not wait on.