You can customize the logo that appears at the top of your course pages through the Design & Visibility settings.
To change your course logo:
Navigate to your course settings, then open the Design & Visibility tab.
Click on Customize Quickly.
Under the Logo section, click Browse to select an image from your account's media library.
If your logo hasn’t been uploaded yet, click Upload at the top left of the library window to add it.
Note: If you’ve enabled Customize for all pages in the page editor:
The logo set in Theme Customization (under Design & Visibility) will no longer apply.
You will need to edit the header of each course page directly in the page editor to change or add the logo.