See Brogan's first post on how to make Page nodes (you have to be an administrator and have the "Manage nodes" permission).
As Brogan also said, if you want to add a link to a Page node to a menu, you either have to edit the navigation template (you have to be an administrator and have the "Manage styles, style properties, and templates" permission) or alternatively use an add-on such as Nodes as Tabs (which you can find in the Resources section on this site).