It means you appeal if the decision is not in your favor. You don't get to sue them for lying. The system assumes both parties are lying, or at least twisting the truth. The examiner will consider the evidence and testimony and decide who is more credible. If they are claiming misconduct, the burden of proof is on them to show it.
If you provide a little more information about the circumstances of your termination we can give you an opinion of your chances.