Frozen fish food, whether mosquito larvae, artemia or other types, is first defrosted. The required amount is placed in some aquarium water in a cup or other container, and you wait until the food has thawed. Pour off the thawed water. The frozen food can be enriched with vitamins or garlic. If the food is too large, it can also be chopped up. 
The frozen food can then be given to the fish. When feeding, make sure that there are not too many leftovers in the aquarium, otherwise the water quality will suffer.