If you want to get started with minimal fuss and aren't interested in much development, you may want to try getting set up with Docker. This approach will give you an ATF-eRegs instance running in development mode without needing to set up Python, Node, etc.
You will need to first install Docker. This will generally install Docker Compose, but you will need that as well if not. You'll also need to clone the ATF-eRegs repository and then run Docker Compose:
git clone https://github.com/18F/atf-eregs.git
cd atf-eregs
./script/start
This a great deal of time, depending on your hardware. Once it's all done, navigate your browser to http://0.0.0.0:8000/.
If you're tweaking the XML input file, start the server with the following instead:
docker-compose up --build web
You will need to restart this to pick up any asset changes. Run the parser from a separate terminal to populate the database:
docker-compose up parser
After the XML file is modified, re-run this last command and reload the page to see the changes reflected.