You show up at office hours to introduce yourself to the professor whose class you are taking and you say “If you know of any opportunities-- fact-checking, editing, number crunching, indexing-- I’d love to hear about them since I’m so excited to be in this class”.
Done. The professor may ask what skills you have (and hopefully, you have some!) but isn’t going to look askance and ask “Are you a Barnard student or a Columbia student”?
If the classes that you are interested in taking are all graduate level courses (and some may be) it’s unlikely that you’ll be “doing research” as a freshman… you’ll need both content knowledge AND actual skills in order to be useful to any professor!
If you haven’t taken statistics or programming yet in HS-- make that a first semester priority once you get to college. You will be much more useful in a research capacity once you’ve got some skills under your belt!