The following will give you a project that is set up and ready to use (don't forget to use --recurse-submodules or you won't pull down some of the code you need to generate a working site). The hugo server command builds and serves the site. If you just want to build the site, run hugo instead.

git clone --recurse-submodules --depth 1 https://github.com/robocup-junior/erebus-document.git
cd erebus-document
hugo server

The theme is included as a Git submodule:

▶ git submodule
 a053131a4ebf6a59e4e8834a42368e248d98c01d themes/docsy (heads/master)

If you want to do SCSS edits and want to publish these, you need to install PostCSS (not needed for hugo server):

npm install -g postcss-cli

Once you've cloned the site repo, from the repo root folder, run:

hugo server

Please refer to the files in content/en/docs, edit or add to them as needed.