How do you change the title of a site (halcyon theme)?

i have no idea how to change the site title in the hero container (the part in the halcyon theme that says "HALCYON DAYS") or the subtitle + the button text beneath it. changing the site title in the admin panel does nothing. is there something simple that i'm missing here?

@atlas Have a look at /user/config/site.yaml

header:
  title: HALCYON<span>DAYS</span>
  description: An exclusive HTML5/CSS3 freebie by Peter Finlan, for <em>Codrops</em>
  buttons:
    - text: "Back to the article"
      link: "http://tympanus.net/codrops/?p=19439"
      class: "learn-more-btn"

I presume you are starting to explore Grav, maybe it is a good idea to start with the latest code available. The Halcyon theme is from the very early days of Grav and young projects tend to innovate rapidly...

Quark is the most recent theme that gets installed by default.

Are you also familiar with the excellent documentation Grav offers at https://learn.getgrav.org/content?