Use this code as a template and add on a course page via the HTML content block:
The code has the following parts:
<a> .... </a> is the link tag
href attribute sets the URL to link to
target attribute specifies where to open the link; _blank opens the link in a new window or tab
<img> is the image tag
alt is the image alt text
src attribute sets the image URL
<div align="center"> .... <div> centers the image horizontally
Learn more about HTML image syntax here.
How to get the image URL
Open the image in the Library, right click it and select "Copy image address".