A little confused about the contents of my SD Card

I'm planning on installing HBC relatively soon and I read I should rename my current private folder 'privateold'.

But then what do I do with it after I have installed HBC? I mean it has quite a bit of things in it.

Also I have a folder called DCIM which contains JPGs from Animal Crossing. Should I just delete that folder all together?

After you have installed HBC delete the recently added "private" folder (containing bannerbomb) and rename your "privateold" folder back to "private".
Leave the DCIM folder as it is.