If you want a title overlaying the image then add some HTML to the hero content eg.
If you only want an image displayed add a HTML comment eg.
<!-- Blog hero -->
Now give the element some Top and Bottom Padding to give it some height.
Set the Background Image to Custom Image, and select the image you want displayed.
For Display Rules you need to select Blog.
HOWEVER – i recall you have a Header Element set to display the line below your Menu. You will need to delete that or the above and other heros will not work. Instead you can use this CSS to add that underline.