Canvas Guide: Embed Images into Rich Content Editor in Canvas
Adding a banner to a course in Canvas assumes that you have already made a Rich Content Editor page your Home Page in Canvas. If you are not ready, please see the guides below from Canvas that will help you set a Course Home Page.
Follow the instructions on the pages below to create a page, set it as the Front page, and then change the Course Home page to use it.
Here is a little bit more about the different options for your course home page What layout options are available in the Course Home Page as an instructor?