My daughter is 6 years old and when she was born me and her father were not together and being young and stupid I didn't put his name on her birth certificate, now me and her father have got back together and been married for a year is there anyway that I can now put his name on her birth certificate?

You need to check with your local Bureau of Records. It may be a simple matter in your circumstances or you may have to go to court to amend the birth certificate. You might want to consult a Family Law attorney.