You would want to have a Sheriff or Constable to try and serve the Defendant at the last place you knew where the Defendant resided or worked. If that was not found there is a process to do a “Summons by Publication” which is doing it in the newspaper, but you just cannot do that on your own you will need to get approval from the court with a Motion for Service by Alternate Means. It is a process that you want to either have an attorney do or make sure you satisfy the requirements with the court.