Add blog category page


I want to add a category page to my blog, like this: (blog start page with a category ’filter’ using reference fields and a few featured blog posts in every category) (shows blog post previews in this category) (entire blog post)

How do I add this extra step between the blog start page and the final page showing the entire blog post? I think I know how to do the filter after watching a tutorial but I don’t know how to add this extra page (I know how to add pages in general but not in the CMS).