How can i add feature image credit text?

Hello

How can i add feature image credit at the bottom of the feature image? https://prnt.sc/rnxj7d

Is it possible to add a box in the editor, like somewhere around the image? https://prnt.sc/rnxk83

Here is the page that I'm working on : https://www.thebestpicks.com/best-action-movies-of-all-time/