Banner Images within Blix

i am having trouble getting my banner to show up within the blix theme.

“Just drop your own banner called ‘header_bg.jpg’ into images/spring_flavour/ and you’re done. Dimensions should be at least 690px x 150px.”

i did exactly this but /spring_flavour is not a folder. what is it and how do i place an image within it?

any help would be greatly appreciated.
thanks, mike

If your custom banne