If a judge agrees, they will give you a court order that states your new legal name. In California, you can ask for a court order to change your legal name.To do this, you file a petition with the court and publish a notice in a newspaper. The first step in legally changing your name is to file a Petition for Name Change with the California court in the county where you reside. Step 1 – Petition For Name Change in Alameda County. To Petition for Change of Name in Alameda County, means to fill out and file a collection of court forms. I went to the Alameda County courthouse to submit my forms, but I don't think they had any stacks of blank forms sitting around to fill out. • Complete the new deed. • Grantor signature needs to be notarized. To change your name as an adult, you need to file a petition in court in the state where you reside.