Once you're enrolled, you can post messages to the list. Just send a message to the email address csci@lists.clarku.edu, and it goes to everyone on the list. Alternatively, you can post messages to the list over the web, if you prefer. Go to the listserv webpage, enter your email address and password, and click on the button "create a new message".
There are other things you can do from the csci listserv webpage
including read messages (in case you're away from your usual mail reader),
change your settings (name, password, how frequently to receive mail, etc),
unsubscribe, and search through
the archives of old mail messages.