You can customize the intro and final message that will be displayed to your form users before and after they have filled and successfully submitted your form. This custom message overrides the default message. You can also add images, formatting, or include links in your intro and final message.
To add a custom message, navigate to your form Settings page then click on the Intro & Post Submission Page tab from the left navigation bar.
Click the Set final message button to include your custom message in the pop-up editor, then click on the Save button to save your composed message.