On the "Pages" tab, click the "Create a new page" button (also you can do this in the second level navigation). You will then be taken to the templates page.
Simply choose a template by clicking on the template icon. Your new page will now be created.
Now enter your "Page name" (This text will be shown in the menu to navigate to your new page).
Enter your "Page URL" (This has to be unique and will show in the URL bar for example "yourdomain.com/yourpageurl").
Select a "Parent page" the default is "No parent (top level) which means the page will be located in the menu on the top level. If you select a parent page your new page will then be located under it's parent page in the menu.
Finally click the "Save details" green button, to save all your new pages details.
Please note at this stage your page isn't live (giving you the chance to add/edit content), once you click "Finish editing" you will be asked if you want to put the page live (this is optional), you can always put the page live at any time please see Hiding or making pages live article.