About programming NDS screens using banks

Hey! I dunno if this is the right forum for this question since it's kind of technical.

I'm learning to program on the DS, and using devkit pro with C. I'm trying to make an artgame program where you draw on the bottom (simple, with the stylus and lines of pixels) and that part works great.

But on the top, I want there to be a background image that has real text on top of it, also I want to be able to change the background around. (there's a character on top who talks to you through the text box).

Can someone help me figure this out? I read something about using banks, but I really don't get how the banks are linked to the screens.

Also, if this is not the right forum, can you please point me to another forum where people talk about this kind of thing?

THANKS!
CM

Whups, when I wrote "on the top" I meant on the top screen! :P