You can basically use them like green lentils. I always soak them overnight before cooking though they also cook up quickly without soaking.
One very simple but delicious way to make them is: boil them in enough water to make them soupy (sorry I don't remember the amounts) with a little turmeric, then puree. Saute some cumin seeds in butter and then mix in to the ready soup. Serve with bread.
Usually nowadays I make them into a hearty soup with bone broth, onions, garlic, root veggies, a green, and some dried herbs (rosemary, thyme, parsley, sage, marjoram, bay leaf, etc.).