Update README with Docker Hub push details

Author: laylark

README.md

@@ -20,6 +20,7 @@ Be the change et al if Windows is your main and you wanna [raise a PR](CONTRIBUT
   * [Setup](#setup)
   * [Usage](#usage)
     * [Mac and Linux users](#mac-and-linux-users)
+  * [Pushing to Docker Hub with CI](#pushing-to-docker-hub-with-ci)
   * [TODO](#todo)
 
 ## Setup
@@ -37,6 +38,19 @@ Be the change et al if Windows is your main and you wanna [raise a PR](CONTRIBUT
 ### Mac and Linux users
 Development environments and tooling are first-class citizens on macOS and *nix. For Windows faithfuls, please setup [WSL](markdown/wsl.md).
 
+## Pushing to Docker Hub with CI
+Docker Hub is a cloud-based repository in which Docker users and partners create, test, store and distribute container images. Docker images are pushed to Docker Hub through the docker push command. A single Docker Hub repository can hold many Docker images (stored as tags).
+
+Automated CI is implemented via GitHub Actions to build and push this repository's image to Docker Hub in `/.github/workflows/push.yml`.
+
+### What you need to modify in this file
+
+* Look for `images: your-username/your-image-name` and change to your respective Docker Hub username and image name.
+* Add repository secrets for `DOCKERHUB_TOKEN` and `DOCKERHUB_USERNAME` on this repository on GitHub.
+  * Here are the [instructions to create a token](https://docs.docker.com/docker-hub/access-tokens/#create-an-access-token).
+
+Here are the [instructions to disable this action](https://docs.github.com/en/actions/managing-workflow-runs/disabling-and-enabling-a-workflow) if you don't want this feature.
+
 ## TODO
 * [Open Issues](https://github.com/pythoninthegrass/python_template/issues)
 * Markdown automation