Creating a blog for a particular category rather than all posts?

Can anyone shed any light on how I can have a blog page with Zerif-lite which displays a particular category?

I have created pages using the two blog templates and they display all posts by default.

I see there is an archive.php template in the theme folder, but it doesn’t seem to be used.

What I’m actually trying to do is make a mod to the blog template so that I can display the category title and description at the top – I’ll probably still use an “all posts” category, but at the moment if I try to do the template mod nothing displays.

It’s a guess at the moment that because there is no category set on the page, I can’t display the category title and description.

Thanks.