I was equally confused on this lol. You cant do it until you're legally married, so make sure whoever is in charge of your marriage license gets it mailed asap after the wedding! The signed & sealed copy should be mailed to you within 2 weeks after the wedding. Take that certificate and go file for a new SS card. They will give you a receipt for this. So now you have your SS receipt and your marriage certificate. Take these things and your old DL to the Driver's License office and file for a new name!!!

You now officially have a new name!!! Now you can go and change your insurances/tax forms/credit cards/bank accounts/etc.....its a BIG pain in the rear lol...but still fun!