How to insert image into headers

How would I insert image from my images into a header. Or banner at top of page.
Does it work if I have a theme associated?
How can it be applied to every page?

The header file contains all the beginning/header content that is common for all pages of the website, such as the head tag and navigation. In a similar way, the footer file contains the structure for the footer. To access the header and footer files go to "Settings" and then "Administrator".

On this page you will find the "Theme Editor". In the list click on "Header". This file is an HTML file. You can learn how to insert an image here: https://www.w3schools.com/html/html_images.asp