​To create a new page,

• Go to the website you want to add a new page
  
• Select Add a Page from the admin dropdown
  
  
  
  You can also create a new page in Pages library:
  
  
• Go to Site Contents
  
  
• Open Pages library
  
• Select the Files tab on the ribbon
• Click on New Document
  
  
  
• Enter the new page name and click Create (View File Naming Convention)
  
  
  
• The new page will open for you to start editing.
• Edit the page title in the Title field
• Edit the page content
  
  Note: Page Titles are different than page names: page titles appear on top of the web pages, they should contain spaces. Page names are file names, they should not contain spaces.

  
  The link to the newly created page is automatically placed on the current site navigation bar after you published it.

  You could disable this feature in the Navigation Settings and add links manually to the current site navigation. There are pages you want to create links in the page content and don't want them to automatically show on the left navigation. (View Modifying navigation / Current navigation)