In WordPress, a Page isn’t just a webpage, it is content type for static content. Most of the webpages on your site will be a Page.

Create a new Page
Use the "+New" menu, then select Page. Every Page will need a title and content. A Featured Image will be used to visually represent the page. The Excerpt can provide custom preview of content for the Page, useful for

Set the Featured Image (banner)
From the Edit view, click Set featured image, then either select the image from the Media Library, or upload a new image (you can drag and drop from your desktop). The size and aspect ratio of the Featured Image determines how it is displayed. The image will be a banner across the top of the page if:

  • it is at least 1000px wide
  • it is at least 1.5 times wide than it is tall (i.e., it is short and wide)