By now, you should have received in your welcome packs the very beautiful Very Helpful Handbook - if not, it will be waiting for you in your halls when you arrive and is available to browse online here: https://www.imperialcollegeunion.org/welcome/handbooks-201314/very-helpful-handbook-201314.
From my time at Imperial, I can definitely testify to the fact that often your own well-being and academic performance are closely linked - when one suffers the other often follows suit. I'm sure at this time of year, in the run up to Welcome Week, the last thing on your mind is what to do should anything go wrong whilst you're at university. However, should anything go wrong, I can promise you that the last thing you'd want to do is run around searching for this information if you're already stressed or upset.
So, to avoid unnecessary worry and to make the most out of your time at Imperial - make sure you take the Handbook to university and keep it in a safe place when you arrive!