2. Click Header in the Layout.
3. Have the url of the image you want to use handy.
4. Type or paste or Browse for the url into one of the two Image boxes,
5. Either an image on your computer or one already hosted on the Web.
6. You can choose to add the photo Behind the Title and Description or
7. You can Replace the Title and Description with the photo.
8. Be sure to Save Changes.
I can't emphasize how much easier the method above is!Below is the old (Classic) method
This method still useable and ultimately more flexible (but you may be well satisfied with the first method above):
The code you'd look for to put a graphic into the header seems to come from a variety of locations in your template. It might go in the #header or #header-wrapper. The method I usually use is to locate a background url that already exists like these: