Hi,
The best way to display a filtered list of SEBLOD contents is to use a SEBLOD search and display it through a menu item, a module or inside a SEBLOD content (use a CCK module or CCK list field).
In your SEBLOD search, you can set the 'article category id' as filter with "11,12" as default value so only articles in these 2 categories will be retrieved.
For the list template, juste use a basic 'List' template : http://www.seblod.com/products/62 and add the fields you want to displayed to it.
If you need a custom layout for every content, you can use a position override.
If your goal is to manage content (add/edit/view), you can take a look to the manual links below.
Olivier