How do I add a tracking script to the iframe of the contact form?

I have a Google Analytics tracking code that I want to add to a client's form. How do I do this in JotForm? They do not have a thank you page.

Please see the guide below with regards to Google Analytics tracking:

https://www.jotform.com/help/1076-how-to-track-online-form-submissions-using-google-analytics