Adding background photo in Impact theme

Hi! I’ve been using the Impact WordPress theme for my blog and making small tweaks to it, as seen at https://www.hlswatch.com/. The final change that I want to make is to modify the header so that instead of a single-color background, it has a subtle picture behind it, as found here (it’s a half-shade off color but correctly sized):

https://www.hlswatch.com/sitepics/background.jpg

But I can’t quite figure out how to modify the header.php code to make this work. I can make the old header and the new header appear consecutively, but not the new background with the title (and the URL link to the website, not the jpg) in front of it.

Any advice?

Thanks in advance for any tips!

Chris
[email protected]