Hi, you will need to have your code built into a Docker image and then pushed to Docker hub.
so you replace reactioncommerce/reaction to yourdockerhubusername/dockerrepo:yourtag
The default tag is latest, so if you use that tag you won't need to add it at the end, that is why there is no tag in the code.
So if you work locally you need to install docker, and to docker build, then docker push
I have been having trouble getting docker to build on pc and mac, so i am using bitbucket pipelines. It works very well. I am writing a guide for it now. This method works if you use bitbucket for your source control.