If you leave the frat party with him, he'll proposition you. So it's not too difficult 🙂 After Will's class, hang out with anyone in the afternoon, choose to go to the party, then play through until it's time to leave. When you get back to the dorm, he'll ask to hook up. Alternatively, if you hang out with Matt & Leo at night and leave early (right after they ask you to take your shirt off) you can catch him jacking off and end up hooking up that way.