frontend submit jnews_flash_message

add_filter( 'jnews_flash_message', 'frontend_message', 99, 3 );

function frontend_message( $flash_html, $name, $class ) {
    $package_url = ''; /* change to your post package url */
    $new_message = '<div class="' . $class . ' alert alert-dismissible fade in" role="alert">' . strip_tags( $flash_html ) . ' if you want post more upgrade to our <a href="' . $package_url . '"> new plan </a> </div>';
    return $new_message;
}