Modify container
1. Download / Create
Download or create the container you want to use as your base.
2. Modify
Make the changes you want to do to it. It can be anything from adding files to updating software, etc.
3. Commit
The most important part, committing your changes to a new Docker image.
docker commit <name-of-container> <username>/<new-image-name>:<tag>
For example, it might look something like this.
docker commit my-container banjoanton/my-image:latest
4. Push
If you want to push your work to Docker Hub, you can do it like this.
docker push <username>/<new-image-name>
Which, in my case, would look like this.
docker push banjoanton/my-image