As shown above this screen allows you to automatically generate a php snippet to protect a web page.

Access Level

Use the drop down to select either an access level, "specific user only" or select "members only" if you do not wish to restrict access to a specific user or access level.

Username

If you have selected "specific user only"

enter the username of the only user who will be allowed access to the page. In all other cases this field can be left blank.

The resulting screen will show you a text area containing the code to protect a page with the access restrictions you have specified. Just copy the code and paste it into the very begining of your html document to restrict access to it.