redwing studio has a detailed description how to set up a Page in your WordPress blog so that only logged in users can see the content. You can restrict access to a page by making it private, or by using a Role Manager plugin, but this method allows the following:
- The Page shows up on the navigation bar (it doesn’t with the other methods)
- If a user tries to view it and is not logged in, you can have the page display whatever you want, such as a login form and/or a message telling them they must log in to see the content (the page just appears blank with the other methods)
To accomplish this, you need to create a unique Page template, and modify the code.
