How to add images in my Slideshow?

Hello!

I bought a premium theme and i really cant add images in my slideshow gallery. I have tried to add it with featured image, with sticky post but no success. I have set the category for my slideshow from my theme settings but i no image is desplayed… There is the code about adding the image in slide show:

<?php
 $files = get_children("post_parent=$id&post_type=attachment&post_mime_type=image&orderby=menu_order&order=ASC");
if($files){ // dos
        $keys = array_keys($files);
        $num=$keys[0];
        $img=wp_get_attachment_url($num);
	  ?>
        <?php $theimage = ''.get_bloginfo("template_url").'/thumb.php?src='.$img.'&w=960&h=350&zc=1&q=90&cropfrom=topcenter'; ?>
        <?php } else { //dos ?>
        <?php $theimage =''.get_bloginfo('template_url').'/thumb.php?src='.get_bloginfo('template_url').'/pix/default/default_carousel.png&w=960&h=350&zc=1&q=90&cropfrom=topcenter';?>
        <?php }  //dos ?>
        <div class="item item_<?php echo $i; ?>" style="background-image:url(<?php echo $theimage; ?>)">
        <img src="<?php echo $theimage; ?>" width="960" height="350" alt="<?php the_title_attribute(); ?>" />
        </div>
        <?php endforeach; ?>
      </div>

I am new in wordpress. Can anyone help me and tell me how to add the images? Thanks a lot..!