Appeal deadline questions after an unemployment denial, payroll clerk here

My claim was denied after 12 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. 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.