Log into your HSU email account and go to the Google Groups homepage. Click on the "Create a group" button in the upper right corner of the "My groups" box.
Creating a group is a two-step process. First, you name your group, create an email address for it, set the types of access to be allowed (Public, Team, Announcement-only, Restricted), and enter a description of the group. Once that's done, you can start inviting people by entering their email addresses. That's really all there is to it.