How do I make pages available to logged in users and not the public?

Currently I Password Protect pages while I am developing them so that tehy are not available to the public but I am getting ready to go live and while some pages should be public many need to be kept protected and only available to people who log in. How do I go about setting that up. I have downloaded the Memebership plugin but dont know how to integrate into my site so that the pages are not available to the public