First of all, you have to buy soybeans. At some supermarkets you can find fresh soybeans/edamame in the produce section. If your supermarket doesn't offer them fresh, you can almost always find them in the frozen section with the other frozen vegetables. You should feel free to buy either shelled or un-shelled soy beans depending on your preference (I personally enjoy shelled edamame since it is fun to shell while eating).
Cooking the soybeans is very straightforward and fast. You just boil a small pot of water and then add the soybeans to the water (let it come to a boil again), and then let the soybeans cook for a few minutes. For frozen soybeans cooking takes about 5 minutes, and for fresh soybeans, cooking takes about 2 minutes. Then, you take the soy beans out of the pot, drain them, place on a plate, and then salt them to taste.
Soybeans are good for you and low in calorie. If you eat 10 pods, you are eating approximately 29 calories, and 1 weight watchers point. If you eat half a cup shelled (75g of just the edible part), it comes out to 120 calories, or 2 WW points (not to mention 12g of protein!).
By the way - edamame don't have to be eaten alone! You can also add them to salads or even sandwiches for an extra crunch, or eat them as a side dish with your lunch or dinner.