Both work. If fresh, the kernels can be removed from the corn cob, whether raw or cooked. If frozen, let them thaw in a colander for about 30 minutes, shaking it a few times. Then cook them according to package directions and spread them out in a single layer on a baking sheet to cool. If it simplifies things, note that 300-350 g (10-12 oz) beans are needed for a single batch.