well it should have been done after marriage but if not for any reason just contact a few sights or again go to your local courthouse where depending on your income they will charge or not,it shouldn't be more than 300.00 give or take. You will need a copy of your marraige certificate to change your name. Many places offer the name change as part of the overal legal marraige process. You will need to change your name with the SSA and any other places you have accounts with. 1stoplegal.com has name change forms for each state. The fees involved vary from place to place, so you will need to check with your local county clerk.