When you are logged in to MovieStarPlanet2, click on Game Options (the cogwheel), and then My Account
Note that Guest accounts cannot use this feature. You need to register your username/account and create a password before you can add your email. Once you have chosen your password, simply follow the steps described above.
If you are under 13:
All you need to know about the Parental Control Center you can find in the articles below:
What is the Parental Control Center?
How do I use the Parental Control Center?