Start at the plain end (the opposite side from the power jack) with the spudger. Carefully pry slightly up and away.
Once you have the end opened up, use the credit card to hold it open.
When you have the entire end separated, carefully pry the sides out and away along the adjoining two sides, working your way towards the end with the power jack. Save that end for last, it should lift away when you're done with the other sides.