Shuttershot theme – sidebar sponsors

I am using the Shuttershot theme at earthworkspc.org. The theme comes built in with a ‘Sponsors’ section on the sidebar (I have altered the text to display ‘Partners’. I cannot find any documentation on how to add images to the grid on the sidebar in order to actually display my partners logos. I have searched sidebar.php but I am no coder, and can’t seem to find out how to add an image url or to upload an image.

Thank you!