Reminder e-mails not sending

I don't want confirmation e-mails sending as I schedule all the appointments of my clients from the back end several months in advance and don't want my clients' inboxes to be spammed.

However, I would like for Reminder e-mails to send 48 hours in advance of their appointments. The only problem is, they aren't sending. I checked the logs and asked my clients, nothing has sent.

Is this a matter of setting up a Cron Job (of which I have no experience)? I have "Send Reminder E-mail to the Client" set as "Yes", "Auto-Confirm" as "Yes", but "Send Confirmation E-mail" set to "No".