Adding static image to page title

I’m pretty happy with the Twenty Seventeen theme so far, but the headers drive me up a wall. If the header looks OK on the home page, it’s going to look like crap everywhere else, and vice versa.

Anyway, I learned how to adjust the height of the home page header and made an image that does look fairly nice everywhere (I think).

But I think it would look even better if I erased the light bulb, then inserted an image of a light bulb inside the div that contains the page title and subtitle. Imagine a light bulb floating just beyond the right margin of “KPow Books, Knowledge is Power.”

Can anyone tell me if this can be done? If so, could you tell me what steps to follow?

I’m reasonably proficient in HTML and CSS. So if someone can tell me what page/file I need to open and how to open it online, I can experiment until I get it right. If there’s no way to access WordPress files online, I can download the file, work on it on my laptop, then upload it again.

Thanks for any tips.

The page I need help with: [log in to see the link]