How to redirect users to thank you page and then back to the form

how do we get the thank you page to populate and then after 3 seconds redirect back to the form.

Thank you for contacting us. 

Inside of this guide you can find how to create a Custom Thank you page with Auto-redirect:

http://www.jotform.com/help/89-Create-a-Custom-Thank-you-page-with-Auto-redirect 

Hope this will help. Let us know if you need further assistance.