Adding attribution for background photo to Home page

Hi, I’ve used someone’s copyrighted photo as the background image for my Expound theme and I need to make an attribution to it on the landing page. How can I do this and keep my posts appearing where I want them to?

The attribution would preferably appear at the bottom of the page, under where the posts actively update.

My blog: https://toppadalist.wordpress.com

Thanks in advance!