Your first page in 5 minutes

1. Start a local web server from the template folder — any one will do:

   php -S localhost:8000
   npx serve .
   python -m http.server 8000

2. Copy the page closest to what you need (for example cards.html) and rename it, say reports.html.
3. Keep everything outside <div class="content"> — the sidebar, top bar and footer — and replace what's inside with your own cards.
4. Change the title in .page-header, and add a link to the new page in the sidebar menu.

Open http://localhost:8000/reports.html and you're done. The page shares the same styles and scripts as every other page.