Thank you for your question.
It seems you are talking about masonry blog posts image which you can change by setting post featured image as described in the following page.
Solution for this topic
Please make the header transparent as described on the following page.
That made the top header bar show, however the image is still the same. I want my own image, not the lady with the camera – how do I change that image? I have my own selected in the titlebar background image section…?