Quick bit of advice needed.
 
When products are displayed the breadcrumb appears at the top of the page.
 
In the breadcrumb we have a link to products Home Page >> Products
 
When you click the Products link I get the Products category which is blank. How do I assign my items to the products category
 
or
 
How do I change the default landing page for products.php

 
This is called 'Top' category, you can put product in it using 'Categories' link below each product:
http://www.viart.com/assign_categories.html
  
If you're using version 4.0 on Dashboard > Products > Products & Categories you should see a link at the top 'Custom Layout' - click on it, select 'Layout Type - Override page layout for this category only' and add the blocks you wish to show up on products.php page.
 
Regards,
ViArt Support