Start your containers...
docker-compose up &
As you edit a document it will compile and reload in the browser
To view your local development version go to
http://localhost:8000
All of the markdown files are in the docs folder. To update an existing page simply edit the *.md file. To add a new page create a new .md file and put in it the docs folder. To get it to show up in the main menu you need to edit the mkdocs.yml file. That's all you need to get going.
See the MkDocs documentation for more help on how to use MkDocs