Hi Tristan,
If the actual category posts are fine, and you just seek to add sections, such as Hero, Masthead, etc., you may do this via Dashboard > PageLines > Drag & Drop > Page Templates or Content Area (depending on whether these need to be full-width or with sidebars next to them).
For full width, click Page Templates then Category. Add sections you want, like Hero, from Available Sections to Active Sections.
For sections with sidebars next to them, do the same thing under Content Area > Category
Because these are special pages, you can edit the content you want to add to them via Dashboard > PageLines > Page Options > Category Page > then select the section you added. There, you can customize the section, adding whatever content format fits the section.