How to enable internet traffic logging in OpenVpn?

I am currently ruing a VPN server for my school without any data logging.

However, despite many waings not to do illegal stuff, I have now received a DMCA notice for torrenting and I think that I need to start logging some inteet data to find out who is behind this.

I am still quite new to OpenVpn and its works, so I was wondering if anyone knew how to do this?

Ideally this would be some basic information as to which users coected to which sites/downloaded files.

Thanks!