1. If you have information/evidence that a person was wrongfully convicted, then contact the police department and the defendant's defense attorney. The defense attorney's contact information can be found in the court records (call the court and ask or look on-line).
2. If you are trying to help a person convicted, then you should contact an appellate attorney to assist you.
Either way, this is not a simple procedure. Your best bet is to contact a local attorney that handles criminal defense appellate work. Good luck.