Background color and image won’t change in Kokoro

Thank you kindly to anyone who can help this newbie. I just started the WordPress journey a few days ago. I’m working with the Kokoro theme. It seemingly allows you to change the background color and image, but when I try to do that, nothing appears. I don’t know how to code at all. I’m happy to download something that can help, but I didn’t want to just start adding things willy nilly. Again, thank you so much for your help!

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