How do I receive the completed form from a submission?

After somebody submits their completed form, how do I view the "Thank you" and their completed form?

If configured, you should receive the submissions through email.

https://www.jotform.com/help/25-Setting-Up-Email-Notifications 

You can also access the form submissions page to view the entire form submissions:

https://www.jotform.com/help/269-How-to-View-Form-Submissions