That's a great question and probably a challenge that a lot of your peers are experiencing too. College is a unique experience in that it offers an overwhelming number of extracurricular activities. The best place to start is to look for clubs or activities that you're interested in. If you think you might want to do some financial planning, join the investment club. Want to give back to the community in some way? Find an organization on campus with which to volunteer. Do you like giving advice to prospective students? Try to get involved in the admissions office. Choosing things that you're interested in will naturally link you to people with similar interests and goals. Starting new things is never easy but it's a big part of making the most out of your college experience.
I am not a particularly extroverted person, but I did some things outside of my comfort zone during college and I think they paid off. You don't have to start with any radical changes. You may consider trying a very simple exercise: every day, try to talk to at least one person you don't know. You don't have to get the person's life story, just exchange some pleasantries. You never know who you might meet or where that conversation could take you.
I hope this helps. Good luck!