Scrapebox is a complicated little tool when you start looking at it. Trust me though, after you fool with it patiently you'll start to understand all its buttons. I'm not sure I understand your question though. To use the custom footprint basically just start typing a query into the textbox underneath the word Harvester at the top left of scrapebox.
Like you could type "inurl:Ringtones" and that would be a custom footprint that saves.
You can then stick in additional keywords in the keywords box, and then hit "start harvesting". You might want to make sure you're using proxies, or not. It's something you need to learn about.
I recommend watching all those videos Scrapebox mentions for tutorials.
Good luck.
