Can someone give me Instructions. Where I can find the Dungeon Key? ( if you can please with pictures)
They can be bought in some of the dungeons - chapel and cardobard to be exact. Besides that they can drop as loot on later floors in those dungeons.
If you want to cheese a bit, you can gather about 100-200 bucks, go to those dungeons and hope for the right vendor to spawn. Then return to the sewers with the keys and open the big doors - they usually have better loot than chests.