Name Changes are filed in District Court, in the county where you reside. Generally a Petition for Name Change and an Order for Name Change must be completed.An additional form is required to make changes to officers, members, and managers with the Office of the Secretary of State. You can file an application to change your legal name in any district court in Washington. The person requesting a name change is called the "petitioner." The first step to getting a legal name change in Washington State is applying for a marriage license. To change your name, you'll need to fill out Form SS-5. The first formal step in changing your name is to file a Petition for Change of Name in the Superior Court of the county where you reside. You have to go to the courthouse where you live and pay for and then fill out the name change application. You have to fill out a name change affidavit; and file it with the court.