How to create a docker dev environment for a REST API and client website

I have 2 websites that work in tandem. One is a REST API and the other is the client website that uses it. My REST API needs to be running in order for the client to work. Each has its own git repo.

How do I create a dev environment that will contain both sites?

What have you done already? Did you do the basics like Internet research on the topic, checking forums and reading some tutorials or watching them on YouTube?

I would expect this has been explained many times before, what is your specific question or challenge?