To add your own preamble in Sphinx. Create your own sty files with the LaTex edits and additions you want. Let's call these first.sty, second.sty. Now, modify the conf.py file ref. Sphinx-doc latex preamble
Basically, for the example.
latex_additional_files = ['first.sty', 'second.sty']
latex_elements = {
'preamble': r'\usepackage{first}',
'preamble': r'\usepackage{second}',
}
Run the following steps and verify the *.sty files show up in your buid/sphinx/latex directory, and your output includes your changes.
python setup.py build_sphinx -b latex
cd build/sphinx/latex
make