In English, a person is almost never referred to as "it". If you know that the person is male, say "he", and if you know the person is female, say "she". If you don't know, that gets into the whole subject of what pronouns to use for unknown gender, which has been discussed at length in response to other questions on this site.
"It" IS used to refer to a person in some special cases. The main one is when we need a pronoun as a place holder to connect to a noun. For example, "A friend of yours called yesterday." "Oh? Who was IT?" Especially if the point is to discuss whether the person is male or female. Like, "Alice had a baby." "Is IT a boy or a girl?" Saying "Is he a boy or a girl would seem a bit of a paradox.