My question involves name change laws in the State of: Califonia

Hello, My husband has been in my daughters life since she was 9 months old. This is the only father she knows. She is 8 and wants nothing more than to have the same last name as him. Her biological father is not on the birth certificate she has my step fathers last name and he has never once supported her. I do not know where he is at or how to get a hold of him. What steps do I have to take to change her last name. Or is adoption an available option for my husband?