Need Help with Header Image

Hello everyone. I want to add a small image to the top right corner of my blog, which uses the Plainscape theme.

Here is the image uploaded as a static page on my blog:

https://www.thatsombercity.com/?page_id=10

The image would be above the search box/button and have the roughly same width as the search box/button.

How do I do this? I assume I need to change the header.php code. Can anyone help me? I would greatly appreciate it.

Thank you.

https://www.thatsombercity.com/

(Posted yesterday in “Themes,” but perhaps this is the appropriate forum for this question.)