how do you get a divorce when the other party is nowhere to be found..have not seen spouse for over 45 years

You will need to have your attorney perform a diligent search, and, if unsuccessful, you can apply for permission to serve by alternate means (publication).

You will need to make a motion for alternative service and show the court that you have looked for your spouse by contacting the post office, board of elections and all the branches of the military (for starters). You will make a motion to ask the court to let you publish the notice of the divorce. This way, you can proceed with the divorce without your spouse. This is complicated and you might want to hire a lawyer to help you get it done correctly. Good luck!