如何在HTML中为此站点添加图像在另一个图像上？

I want to add an image on top of another image in this site. The HTML codes are found here. There is already a string of javascript code present that functions to make the bigger uploaded photo as a canvas to be typed on it. Now the problem is I cannot seem to place the smaller image on top of the canvas photo just like adding text on it. I want to add an image on top of another image