First you will need to create a DockerHub account, once you are done with that login to your account through the terminal of the system where you are working with docker, use the below command:
$ docker login --username=yourhubusername [email protected]
You will get the below message on successfull login:
WARNING: login credentials saved in /home/username/.docker/config.json Login Succeeded
Now use the below the command to list down all the images present in your system:
$ docker images
Find the image you want to push to dockerhub and then tag it using the below command:
$ docker tag bb38976d03cf yourhubusername/custom_image:latest
Here make sure that you tag your image in such a manner :
Then you can push your image using the below command:
$ docker push yourhubusername/custom_image:latest
Then go ahead and check your dockerhub, you should find your custom image uploaded to it.
Hope this helped :)
If you are looking for resources to study from or any help from a trainer try the docker training course.