Change redirect after form submission

Because we can't use Zendesk forms without enabling the Help Center (which is not yet ready), I am trying to remove from our form all references/links to the Help Center.  I've edited the theme code to remove the breadcrumbs and the logo hyperlink.  I think all that is left to do is to stop the form from redirecting users back to the Help Center after they submit a request.  

How can I change where users are directed after they submit a request?