I think it depends on how much knowledge they're going to need. If it's just a simple idea of how it works then you could put a simple guide (or make a simple webpage) for topic 0, the heading, in your course. If it's an institution front page then there's usually space to modify the greeting (right-hand side on the standard Moodle). I've made up a couple of Word documents I link to so students can see how to operate the system (basic version) and gain better understanding of/access to e-learning (advanced version).
Hope that helps,