Not *easy*!
Plugin
https://wordpress.org/plugins/woosidebars/
Editing function.php
remove_action( 'storefront_sidebar', 'storefront_get_sidebar' );
Custom CSS
#primary {
width: 100%;
}
More reading
https://wordpress.org/support/topic/remove-sidebar-on-product-page
https://docs.woothemes.com/document/woosidebars-2/