How to add a shape or png to a chart?

Hello,

I have a chart showing storm surges and I would like to place the figure of a human in the chart to show relative height. However, I am having issues doing this with shapes and cannot figure out a way to overlay an image with a transparent background. I have watched a few tutorials on shapes and have had trouble understanding the basics of how to assign a shape to a table or create a table.

Thanks!