No image when share website

Nope, that is what I would have thought would be the best way.

You might want to look here
https://jetpack.me/2013/07/12/add-a-default-image-open-graph-tag-on-home-page/

If you use a child theme, in your child themes functions.php file you can add this code:

function fb_home_image( $tags ) {
    if ( is_home() || is_front_page() ) {
        // Remove the default blank image added by Jetpack
        unset( $tags['og:image'] );

        $fb_home_img = 'YOUR_IMAGE_URL';
        $tags['og:image'] = esc_url( $fb_home_img );
    }
    return $tags;
}
add_filter( 'jetpack_open_graph_tags', 'fb_home_image' );

Obviously, where it says “YOUR_IMAGE_URL” you will have to copy the file path for the image you want to use, and paste it between those code ticks.

The post above is obviously dependant upon you using jetpack