Having a smaller image link to a larger image is known as thumbnailing. You can link an image to another image by taking advantage of Image Placeholders from within an Article's Content or Summary field. Use the :url modifier of image placeholders to insert the full url to the uploaded image:

<a href="***image2:url***" target="blank"><img src="***image1:url***"></a>
This would treat image 1 as a thumbnail, linking it to image 2, the larger image.

More tips & tricks coming soon!