There is no such thing as a dim question, just dim answers.
Built in to OS X is a fairly capable Help system. It contains a bunch of information which is, usually, easily accessible. Just type in what you want to do and a choice of answers should appear.
Typing in Screen saver passwords produced the following answer to your question:
For extra security, you can require a password to turn off a screen saver. In System Preferences, click Security and select "Require password to wake this computer from sleep or screen saver."
Pretty neat, Huh.
Not everything is in there, so ask when you can't find an answer