If you haven't already, create a DockerHub account and install Docker on your computer. You'll want to look for the Docker Community Edition for your operating system. It sometimes takes some time for Docker to start, especially the first time. Once Docker starts, it won't open a window; you'll just see a little whale and container icon in one of your computers toolbars. In order to actually use Docker, you'll need to open a command line program (like Terminal, or Command Prompt) and run commands there.