You will need Python 3 installed as well as pip3. The mkdocs website will explain how to do this, and how to install mkdocs. This guide was developed on Python 3.9.
After cloning the repository, you can install all the needed dependancies (including mkdocs) with this command, ran in the project's directory: pip3 install --user -r requirements.txt
Please take some time to familiarize yourself with mkdocs. The site will detail everything for you.