How do I send an email to people who filled my the form?

You can do that by creating an Autoresponder Email. Here's a guide: 

1. In the Form Builder, click the Emails button.

2. In the Emails wizard, click the Create New Email button.

3. Select Autoresponder Email to send an email the person who fills your form.

4. Make sure you have an email field on your form.

Helpful guides:
https://www.jotform.com/help/26-Creating-a-Form-Autoresponder
https://www.jotform.com/help/30-Explanation-of-Email-Notification-and-Autoresponder-Settings

Hope that helps. Thank you.