Panino : show 1 category in the single-blog-page

Hello support,

I have a question about the theme Panino,
i was trying to create some extra templates, that show only one category of posts.
Because i want to use the same layout as the single-blog-page i copied most of that code.
Now I know that the code
"$main->add_element("Posts", array ("
is the code to show the content on the page, is it possible to use the code has_category.
Because i tried and failed.
What do i do wrong.

Thanks for the feedback