You must have "Full Access" or "Limited Access - Website" permissions to add pages.
Sign in to the site and turn on Edit Mode.
Underneath Edit Mode, click Pages.
Select Sub Pages or Main Menu, depending on where the page needs to be added.
Main Menu is the horizontal list of page links at the top of your site in the main navigation.
Sub Pages appear in the dropdown menu under a page listed in the Main Menu.
Click Add New Page.
Choose the Page Type from the list of options.
Input the necessary and mandatory information, then click Create and Go To Page.