I finally did find where to make the changes to direct the last box below the slide banner to a category. It wasn't easy but i'm learning.

For other DIY like me make changes to this file

includes/languages/english/html_includes/winchester_black/define_main_page.php

in my case I changed the line that say:

<a href="index.php?main_page=product_info&amp;cPath=8&amp;products_id=18" ><img src="includes/templates/winchester_black/images/home1.png" class="home-img" alt="your product title" /></a>

to this:

<a href="index.php?main_page=index&cPath=17" ><img src="includes/templates/winchester_black/images/home1.png" class="home-img" alt="Bargain Bin" /></a>

Please note that "index&cPath=17" is the ID for my category.

Hope it helps someone else.