First time ripping sprites, need a little advice

I'm trying to extract the rest of the sprites from bleach: dark souls on the DS. I have the ROM and the save file with all the characters unlocked, but I'm not sure exactly where to start to rip the sprites. Can anyone help me out?

EDIT: I know I'm a noob about this but google isn't helping at all. I really can't figure out where to start. Is it possible to do using DeSmUmE? Can someone please point me in the right direction to get started?