You cannot begin using your new name once you have filed the papers. There are several steps that must be completed to complete a name change and it will take a minimum of 60 days to legally change your name.
You cannot legally use the name until the judge grants the name change petition. After you file the case, publication must be made in the newspaper and a hearing in court is held, so generally, it takes about 3-4 months.
Advice on this forum is for informational purposes only and should never be mistaken as a substitute for legal advice. If you are in need of legal advice, you should consult local legal counsel.