where to sign up for formal recruitment?

First off definietly sign up for greek rush and make sure you have all the houses checked that you're interested in. This will let them know you're interested and can aleast see some things going on this summer. Even if you don't plan on summer signing anywhere i highly encourage you to check some things out. This is like college football recruitment, they will wine and dine you so why not take it all in.
Secondly, reach out to the houses you're interested in as this will go a long way and create a connection now. It's hard for a house to meet and like you all in the day or two of formal.
Thirdly, contact the ifc recruitment chair and ask how to sign up for formal and so on. He's a good resource and will help you with anything you may need.