How to install SQLalchemy, then connect to managed PostgreSQL DB

I successfully went through this tutorial: https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-gunicorn-and-nginx-on-ubuntu-18-04 Now I’m stuck. Trying to also install SQLalchemy and then connect to a managed PostgreSQL DB. I’d love to see a part two to the above tutorial. An extra bonus would show pulling data from DB and displaying it via a Flask/Ninja2 template. Thanks!