Can someone please help with Cron Jobs?

I keep getting a notification that Cron Jobs are not running or not set up and I have read the "instruction" that is apparently attached to this notification message at least 5 dozen times- it makes no sense to me. Can somebody please help? I took it to chat with Hostgator and they said they fixed it for me but they didn't I still get the same message. I tried to figure it out via CPanel "Cron Jobs" but I have no idea what to put in the "command" section. Any assistance would be greatly appreciated pxpx
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Do you get it how to setup cron? please share with me.