If the person published using a pseudonym, enter his or her real name in the Author field. Make a note of the person's pseudonym in the Title supplement field. For example: Published using the Pseudonym Mark Twain.
There are no consistent rules for when you should cite a pseudonym instead of a real name. If a person is generally known by his or her pseudonym, his or her works are listed under this name (for example, Caravaggio), it is usually fine to cite the person by his or her pseudonym.