Layout Confusion

When making a layout, does anyone know how to put a picture as the background.
I just can't seem to figure it out.
Please, help me!!

I tried taking a picture off of photobucket by bringing the picture up and then pasting the url in the place it says to do so, but when I did that nothing showed. I'm really quite confused and don't want to deal with this right now. All I want is a custom layout, but I seem to fail at doing so.
If anyone has made a layout before or thinks they can figure it out, comment or message me please!
(Iput this random comment here because my entry has to be at least 100 words long)