Backgrounds TOO BIG!!!

GSExtreme

I designed about 12 images and merged them together as one image, following each other....the whole picture is 2.8 MB....how can I make the background change with the actor movement??? I am totally new to this...and also how can I place the enemies in different parts of the image? Also gamesalad tells me the image is too big too handle?? Resolution is 11099 by 640...as all the images are in one image