How to Redirect a Form to a Thank You page
and then to HOME.

Here's what I did.

1. Make a "Thank You" page. Untick 'include in navigation'. Make sure you name the page. (I made mine a child of the Contact page).

2. On the Contact Form, right click > Edit Form Properties. Click SELECT on redirect to: and enter the FULL URL of the Thank You page. (Mine is http://foxhillers.com/mitch/thankyou.html)
Or click on a page in your site and select it, according to Mike K.

3. I also redirected the Thank You page to return automatically to HOME. To do this, go to ThankYou page, right click and select Page Properties > Redirect tab. Click on Link.... in Redirect to: select the HOME page or a page of your choice. Mike K likes to put a note on that page telling folks they will be redirected.