Docker is an execution engine that runs containers as mini virtual machines. Installing it locally will allow you to test your container on your machine before deployment.
Git is the source control manager used by the popular open source hub GitHub. Install it locally to allow you to maintain versions of your code and push them to Orbs.
As part of the deployment process, you will need to open a PR (pull request) to Orbs open source GitHub repo. This will normally require you to have a free GitHub account.