How to change which account is Admin on my Macbook without creating a new account?

My parents set up parental controls but decided to take them off, i can get the admin password. My parents have there own admin account on my computer and then there is mine. How can I change my account to a Admin so I can edit preferences and install applications.|||Open System Preferences, then Users. Click the padlock in the bottom left and type an admin's username and password. Click your name, and you'll see an option to make the user an administrator.