Sign up for a free account: https://hub.docker.com/

Command:

[root@docker ~]# docker login
Username: username
Password: 
Email: [email protected]
WARNING: login credentials saved in /root/.docker/config.json
Login Succeeded

docker login --username=username --password=1234567 [email protected]

source: https://docs.docker.com/reference/commandline/commit/
First you will need to commit a container, then you can push it to the repository

docker commit containerID luke/containername:tag

If you forgot to tage the container before you committed you can do it now

docker images

docker tag ImageID luke/test:tag

docker push luke/test