The “Edit this page” link (top right) opens GitHub's online text editor. Changes made this way will automatically update the site via a webhook - it's great for fixing typos, small changes, etc.
The “Edit this page” link leads to a page where you can “fork” the
repository and edit your copy. Please create a “pull request” to get your
changes incorporated into this site.
If you expect to make more changes, you can also add a new issue on GitHub with your plans and a request for direct edit/commit access as contributor.
For larger changes, it's much more convenient to use Hugo's live preview server mode, which shows the effect of each change as soon as it is saved to file. The basic steps to do this are:
A convenient setup is to keep your editor and browser open, side-by-side.