Denied unemployment, how do I appeal? after 18 years as a graphic designer

My claim was denied after 21 weeks of waiting, and the letter says I have a short window to appeal. It has been a long 21 weeks. I have not done a hearing before and I am nervous. If you have appealed before, what helped you prepare?

Legal aid offices and some workforce centres help with unemployment hearings at no cost. A call is worth it.