Open the “Parental Controls” application from the home screen. If you are prompted for a 4 digit PIN number the default is “0000”.
Controls & Settings guide
The PS Vita Parental Controls can make the handheld console safer for your children by restricting games or videos with mature content, disabling the internet browser and blocking adult sites, and restricting how your child can chat on the PlayStation Network.
The PlayStation VITA console you wish to apply restrictions to.
See more resources and articles to help children stay safe online.