Denied unemployment, how do I appeal? after 17 years as a retail manager

I got a denial letter last week saying I left my job voluntarily, but I was let go as a retail manager. It has been weighing on me all week. 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.