docker login

returns:

Username: peter
Password: 
WARNING! Your password will be stored unencrypted in /root/.docker/config.json.
Configure a credential helper to remove this warning. See
https://docs.docker.com/engine/reference/commandline/login/#credentials-store
 
Login Succeeded

For example, to tag the nginx-instance image:

docker tag 12cefc9b5362 peter/nginx-instance:ubuntu

where:

• 12cefc9b5362 is the ID of the nginx-instance image.
• peter is your Docker Hub username.
• nginx-instance is the name of the image that you want to push.

docker images

returns:

REPOSITORY                 TAG                 IMAGE ID            CREATED             SIZE
peter/nginx-instance       ubuntu              12cefc9b5362        12 minutes ago      158MB
nginx-instance             latest              12cefc9b5362        12 minutes ago      158MB
ubuntu                     20.04               d70eaf7277ea        12 days ago         72.9MB

Push the new image named peter/nginx-instance to the Docker Hub:

docker push peter/nginx-instance

Login to the Docker Hub using your web browser and verify that the nginx-instance image appears in the Repositories.