The forms that come with WebEasy are submitted using the email system running on the computer used to view the web site. Because of this, the act of submitting the form and what happens after submission is complete is not under WebEasy's control.
In order to have a page displayed after form submission, the form must be submitted to a "form mailer" script running on your web server. Hosting providers often make scripts such as this available as part of their hosting packages.