If you know how to create links in Markdown, you can create images, too. The syntax is nearly the same.
The difference is that an image is prefaced with an exclamation point ( ! ), followed by the same two brackets, and a pair of parentheses containing the image URL. Within the image brackets, you can place some "alt text," which is a phrase or sentence that describes the image for the visually impaired.
In the box below, turn the link to an image, and fill out the alt text brackets to say "An image of James B. Hunt Library":
You can also reference local image files for use in websites. For example, if you keep the images you use on your site in a folder labeled images your link would look like this: