My husb and I we're not married when I gave birth to our daughter and he was still awaiting his divorce so we could not give our daughter his last name. Now that we are married we want her to have our family name not my madien name , we need to know all the steps to take in order to change her last name leagaly and on her birt certifacte.

I'm not sure if you will be able to change the birth certificate, because that is the name she was given at birth... but I may be wrong.

The rest you just do the same as when you change your name. You will need to file for a new social security card, present her birth certificate with you and the father listed, and also bring your marriage certificate. That will get her name changed legally... but just like you don't have your birth certificate changed when you get married, I don't think you will be able to get her birth certificate changed.