docs: add DockerHub instructions

Makefile

@@ -83,7 +83,7 @@ docker-push:
 
 docker-run:
 	source .env && \
-	docker run -it -e OPENAI_API_KEY=${OPENAI_API_KEY} -e ENVIRONMENT=prod ${CONTAINER_NAME}
+	docker run -it -e OPENAI_API_KEY=${OPENAI_API_KEY} -e ENVIRONMENT=prod ${DOCKERHUB_USERNAME}/${REPO_NAME}:latest
 
 
 ######################

README.md

@@ -29,16 +29,40 @@ make init    # create a virtual environment
 
 ### Run Python on the command line
 
+1. Activate the Python virtual environment
+
 ```console
 source activate
+```
+
+2. Run the application
+
+```console
 python -m app.hello_world
 ```
 
 ### Build and run with Docker
 
+1. Build your Docker container
+
+```console
+make docker-build   # run Docker compose to containerize your application
+```
+
+2. Run your Docker container
+
+```console
+make docker-run     # run the application as a Docker container
+```
+
+### Push your Docker container to DockerHub
+
+1. set DOCKERHUB_USERNAME and DOCKERHUB_ACCESS_TOKEN in `.env`
+
+2. push the container
+
 ```console
-make build   # run Docker compose to containerize your application
-make run     # run the application as a Docker container
+make docker-push    # run Docker compose to containerize your application
 ```
 
 Sample output: