Could you please tell me exactually how I go about getting a divorce by running an ad in the paper?

This is used only as a last ditch effort when you cannot locate your spouse. It is different in every area. A divorce lawyer can guide you in the right process for your location.

Get the assistance of a competent lawyer; you don't want to mess this up.

You don't get a divorce by putting an ad in the paper. You go to an attorney, have the attorney draw up and file the appropriate paperwork. Then the attorney has to have your husband legally served with the divorce papers. If your attorney is unable to have the papers served through the routine methods- server, certified mail, law enforcement officer- then he may petition to have your husband served by "publication" in the newspaper of your husband's last known address.

Note that if your husband finds out about it after the fact, and can prove that you knew his address, and your attorney doesn't have proof of failed service--it can really get nasty.

My ex-husband lied and told his para-legal that I lived in Arizona (because he was in Yuma in the military.) I have never lived in Arizona. He knew my address, he knew my attorney's address and he had evaded service by the Orange County Sheriff's Department. When we were able to prove this to the Judge, he threw the book at ex-husband.

The posting in the newspaper is only done after a complete search has been done to find and serve the other partner with papers to appear in court. So you hire an attorney , file for divorce in court, try and have the ex served with court papers, if he can not be found, you have it published in accordance with the standards of your local court, and then have a judge rule on the case.