What is the easiest way to get a divorce if I havent seen my partner in over 15 yrs

Please consult with a lawyer who practices family law in your area.  The easiest way to get a divorce would be if the two of you could agree on the terms and your spouse would file a waiver of citation so no service would be necessary.  Of course, you would have to know where your spouse resides if you want to try to do it this way.  If you do not know where your spouse resides, contact his/her family and friends to try to get an address and/or phone number.