What is the "Kamchin" can on the photo and what can I do with its contents?
Kamchin is a mixture of herbs, used for making Persian stews such as Ghormeh Sabzi. In Farsi, Ghormeh means stew and Sabzi means herbs. A basic recipe for Ghormeh Sabzi is:

INGREDIENTS 500g of Beef or Lamb I cup kidney beans 2 onions 500g Kamchin – these are Persian herbs, a mix that is mostly parsley and spinach
METHOD Fry onions Add Kamchin Fry beef 5 – 10 minutes Add 4 cups of water Cook for 2 – 2 ½ hours over low flame. The end result is a thick stew of meat, vegetable and beans. Serve over rice. In this case it was decorated rice.

I found many variations of this basic recipe. Some had a dark green such as spinach or kale while others used potatoes. A Google search will give you a ton of results for Ghormeh Sabzi, and while some don't specify Kamchin, they do call for the same ingredients found in Kamchin.
I would think that the Kamchin could be used for other Persian or Iranian stews, or really in any hearty lamb or beef stew, as it is a nice blend of herbs.