How to show widget in frontend?

Your widget method does not echo anything. If you want content to show up the widget needs to echo content.

function widget( $args, $instance ) {
    extract( $args );

    /* Our variables from the widget settings. */
    if(isset($instance))
    {
        if( isset( $instance[ 'title' ] ) ) {
            $title =                apply_filters( 'widget_title', $instance[ 'title' ] );
            // try this
            echo $title;
        }

        if( isset( $instance[ 'template' ] ) ) {
            $template =             htmlspecialchars_decode( $instance[ 'template' ] );
            // try this
            echo $template;
        }
    }
    
    
}

That is probably not the format you want but it should display your content. Be aware that widgets support several parameters such as $before_title and after_title. While you don’t have to use those, it is generally a good idea.

Reference

http://codex.wordpress.org/Widgets_API