how do it work...

Are you talking about spring or fall? For fall, the only sorority that does open informal recruitment is Delta Gamma, and their pages should have the info on that. Some other sororities do take new members in the fall but usually that's only for people who already have a good relationship with a lot of current members of the chapter and have expressed interest in joining. Also I'm almost certain that fall recruitment of any kind of only for sophomores and older, because they want freshman to go through formal recruitment first

In the spring, everyone goes through formal recruitment so as long as you sign up for that (the link should start being shared in the next few months), you'll get to see all the chapters. You definitely don't need to know someone to get a bid from a specific sorority