Well, for the very basics, you can read through this Twine 2/SugarCube 2 tutorial. After that, I'd recommend at least skimming through the SugarCube 2 documentation. For example, you can read where it explains how to do basic image links in SugarCube. For other sample code see the Twine Wiki.
Now, back to your original question.
If you want to use an HTML <img> element, then you'll need to wrap an HTML <a> element around it to link to the passage you want to go to, like this:
<a data-passage="Passage Name" class="link-internal link-image">
<img src="Image.jpg" style="max-height: 300px">
The "data-passage" property should be set to the name of the passage you want the link to go to, and then just add the "link-internal link-image" classes.
Note that I also set the style on the image to limit the maximum height. If you want to modify the image dimensions you should probably use something like that to avoid distorting the image.
You can also add a "title" property if you want a tooltip with the value of that property to appear when you hover the mouse above the link. Also, setting the "alt" property to a description of the image for blind users is highly recommended.
Hope that helps! :-)