The Littlest JupyterHub has a good overview page on writing documentation, with externals links to the tools used to generate it.
First, create a new environment:
conda create -n plasma-docs -c conda-forge python conda activate plasma-docs
docs folder, run:
python -m pip install -r requirements.txt make html
docs/_build/index.html in a browser to start browsing the documentation.
make html after making any changes to the source.