I realize this conversation was posted a year ago but I wanted to thank all involved because after searching through tutorials and how-to blogs and posts, I finally found this support forum. I had the same issue: a white background would automatically show underneath my logo once I uploaded my file onto my website.
All posts are very descriptive and I was able to make my background banner transparent. I didn’t need to enter codes, just save and upload my pic as png.
So THANK YOU: alukaszewics, ronmerk, and Sakin!
Lynna