Once this is done, the stats are available at: www.domain.com/webstat and are viewable using the domain's ftp username and password.
This didn't work for me initially and I just got an error that the system hadn't run the statistics cron and if it didn't work within 24h, to check with my domain admin... that's me! Well, 24h passed and nothing had changed:
/usr/local/psa/admin/sbin/statistics --calculate-one --domain-name=domain.comAfter a short wait, the process was complete and a pretty awststa page appeared where it should have been all along. I'll just have to wait and see if a) it updates and b) whether this needs to be done for other domains.