OS X El Capitan: Add a managed user
You can’t set up parental controls for administrators or sharing-only users. To set up parental controls for a user, do one of the following:
Create a new user account with parental controls enabled for it.
Convert an existing user account to a managed user with parental controls enabled.
This option converts the account you’re using to a regular, non-administrator account. If this Mac has only one administrator, you’ll also be prompted to create a new administrator to replace the one you’re converting. OS X requires at least one administrator.
If you want limited access for a user on the Mac, but don’t want to add that person as a user, set up a guest user account that you manage with parental controls. For more information, see Set up users on your Mac.