Hi!
On the Layout Options -> Results layout panel you will have to change the Show more results.. url option to I believe ?s={phrase}&post_type=product
http://i.imgur.com/kEmidgM.png
That should trigger the woocommerce override and display the product results page.
Also, you can turn off the Override the default WordPress search results page? option, as it’s not working with the woocommerce engine (woocommerce has its own override).