Put any food that you want to feed in a turkey baster and fire it across it's face, I recommend something like small krill and daphnia but you may want to mix bloodworm in for the first week, the movement as it comes out simulates live food, keep your hands in the water and they gradually recognise your hands as food, then throw away the baster and hand feed.....then mix in all types of food.
Guess the largest food you think they can swallow and then double it, mine takes the biggest chunks of food.