Illustrator :: Exporting To JPEG / PNG With Bleed

I've designed 2 artboards (basically two halves of one image) for a competition entry. Pieces can only be submitted in jpeg or png at 5mb max and using only one file. I've designed it at actual size (approx 4000x1000 mm). I have managed to reduce it and save the whole image as a png file (with a white gap dividng the two panels) I'm now thinking this is amateurish and the required bleed setting may have been lost. So,
 
1. The correct way to crop artwork to each artboard and export artboards to one jpeg or png file.    
2. Maintain bleed settings around each artboard.