If you buy fresh edamame, it should be sold on the stalks like this. Otherwise pulling the pods off of the stalks opens the pods, so they won't stay fresh for too long.
Remove pods from stalk. Boil a pot of salted water - one or two teaspoons for a large pot. When water is boiling, add the edamame pods. Test an individual edamame at around 5-6 minutes and gauge the firmness of the bean. Edamame beans should be firm, yet give to the teeth. Mushy beans means that they are over cooked. Pour beans into a colander. Salt to taste. Serve edamame in the pods, or remove beans from pods. Serve at room temperature or cold.