Instructions
Power on your PlayStation 3 and let it boot to the Cross Media Bar, or XMB, the menu system of the PlayStation 3.
Scroll to the leftmost icon on the XMB, labeled "Users." Select "Create New User" from the drop-down menu that appears.
Enter your desired name, whether it be your online screen name or just your own name.
Select "Okay" once your name is entered to complete the process of creating your own account.