First install python pip, for example:
sudo apt-get install python-pip
Next install Sphinx:
$ sudo port install py36-sphinx
$ sudo port select --set python python36
$ sudo port select --set sphinx py36-sphinx
$ brew install sphinx-doc
$ sudo apt-get install python-sphinx
sudo pip install sphinxcontrib-httpdomain
sudo pip install sphinx_rtd_theme
Make sure you are in the respository root and then run:
make html
Files will be generated in the 'build' folder.