Once someone fills out my form, how do I set it up so that they receive a copy of their submitted form?

You need to create an Autoresponder email. This will allow you to send an auto-reply email to the user who completed the form. Here's a guide: https://www.jotform.com/help/26-Creating-a-Form-Autoresponder.

If you have any questions, let us know. Thank you.