Onclick Submit Code

I have a landing page/squeeze page in Wordpress made with Instabuilder and WP Sales Copy plugins. I need a simple code inserted in the landing page that loads a specified url (which I will provide) when the visitor clicks the submit button to opt into the landing page. Following is an example of how this needs to work. Visitor arrives on landing page and decides to opt-in. They complete the optin form and click submit button, which adds them to the autoresponder and directs them to a thank you page (This is the current setup). The only change needed is that when they click the submit button, a specified url loads in the same window as the landing page.