Install Jeckyll
To install Jekyll, follow the official installation guide at https://jekyllrb.com/docs/installation/.
Don’t use mac’s pre-installed ruby, it is outdated. follow the instructions to install a newer version using a version manager like rbenv or rvm.
Use as a Ruby Gem
Alternatively, you can install the theme as a Ruby Gem, without creating a new site.
Add this line to your Jekyll site’s Gemfile:
gem "just-the-docs"
And add this line to your Jekyll site’s _config.yml:
theme: just-the-docs
And then install all relevant dependencies:
$ bundle
To test your theme, run bundle exec jekyll serve and open your browser at http://localhost:4000. This starts a Jekyll server using your theme. Add pages, documents, data, etc. like normal to test your theme’s contents.