If you know your password and can sign in to PlayStation Network you can change your password yourself.
Go to [Account Management] on your PlayStation system or [Account] on the SEN Account Management website.
For step by step instructions select the device you will be using:
If you have forgotten your password you cannot reset it yourself. Ask the person who looks after the master account to reset it for you from their account.
The master account holder needs to go to [Account Management] > [Parental Controls] on PlayStation system or [Account] > [Sub Accounts] on the SEN Account Management website to change your password.
For step by step instructions select the device that will be used: