Welcome to the forum, alisabti.
We don't use "it's me" for an introduction. If I knock on a door and the person inside the room asks "who is it?", I may respond, if that person knows me, "It's me". Some people feel that the only correct response, assuming that you don't do the sensible thing and give your name, is "It's I", but that sounds very stuffy to most of us.
Student or Learner