NT: update readme with image generation instructions

Author: Joe Cardella

README.md

@@ -4,9 +4,13 @@
 
 This Docker image adds the gke-gcloud-auth-plugin and kubectl to the base `google-cloud-cli:alpine` image.
 
-## Dockerhub Integration
+## Image generation
 
-* To generate new images for the latest google-cloud-cli version, add a new tag off `main` like `398.0.0`
+* To generate new images for the latest google-cloud-cli version:
+* * Go to [Google's container registry](https://console.cloud.google.com/gcr/images/google.com:cloudsdktool/global/google-cloud-cli) and find the latest version.
+* * Update the `src/Dockerfile` and set the docker image tag to the latest version number: ex `399.0.0-alpine`
+* * Commit and tag the main branch with `v` followed by the version number: ex `v399.0.0`
+* * Push the udpates and tag upstream.
 
 ## Security Reports