The "live chat" link (also called Chat with a Librarian) is located underneath the library hours on the library home page, as indicated below.
You may also use the direct link at http://esearch.sc4.edu/247.
Once you've clicked on the Chat with a Librarian option, the next page will have the live chat box on the right hand side of your screen. It looks like this:
To chat, just enter your email address and your question, and a librarian will reply within a minute or so.
If chat is offline, contact SC4 library for assistance.