Write Wordpress shortcode for twitter plugin

I'm having a lot of trouble trying to write a Wordpress shortcode for a twitter plugin. I'm not very familiar with PHP and so I'm really not exactly sure where in the code I should try to implement the shortcode.

<?php 

if ( !class_exists('UNCTwitterTimeline') ) {

class UNCTwitterTimeline {

    public function __construct( $instance ) {

        extract( shortcode_atts( array(
                'id'            => '',
                'width'         => '520',
                'height'        => '600',
                'theme'         => 'light',
                'link_color'    => '#333333',
                'border_color'  => '#e8e8e8',
                'header'        => 'true',
                'footer'        => 'true',
                'border'        => 'true',
                'scrollbar'     => 'true',
                'transparent'   => 'false',
                'tweet_limit'   => '10',
        ), $instance ) );

        $this->id           = $id;
        $this->width        = $width;
        $this->height       = $height;
        $this->theme        = $theme;
        $this->linkColor    = $link_color;
        $this->borderColor  = $border_color;
        $this->tweetLimit   = $tweet_limit;
        $this->chrome       = "";
        $this->chrome       .= ( $header == 'false')        ? 'noheader ' : '';
        $this->chrome       .= ( $footer == 'false')        ? 'nofooter ' : '';
        $this->chrome       .= ( $borders == 'false')       ? 'noborders ' : '';
        $this->chrome       .= ( $scrollbar == 'false')     ? 'noscrollbar ' : '';
        $this->chrome       .= ( $transparent == 'true')    ? 'transparent ' : '';

    }

    public function show() {

        require UNC_TWITTER_PATH . 'views/twitter_timeline.php';

    }
}
}
add_shortcode('twitter', 'UNCTwitterTimeline');

via Chebli Mohamed