How to marry a inmate? In jail.
Your inmate must get permission from the warden - and prison is normally the place where an inmate may get married. Jail marriage does not happen often if at all. Only inmates with long sentences (along with a perfect record while incarcerated) are eligible. Our advice is: if your relationship is strong, marriage is not going to change anything. If you are getting married for other reasons, we would recommend waiting until you can have a proper ceremony.