Rinse the fish in running fresh water to remove the ice from it.  Pat dry the fish with kitchen towel to remove excess moisture.   You can skip thawing if you are short on time and want a quick meal when steaming frozen fish.   Pour a moderate amount of water on the pot.  Place the steam rack on the pot and put the rinsed frozen fish on top.    You may put aromatics on the water like chopped onion and crushed garlic.  You may also sprinkle the fish with salt and lemon juice for flavor.