The first prerequisite to install CircleCI CLI is to have Docker (https://docs.docker.com/install/) installed. To install Docker on your OS, visit the Docker store at https://store.docker.com/search?type=edition&offering=community and click on the Docker CE link which is suitable for your OS or cloud service. Follow the installation instructions on their website.
Make sure that Docker is installed by checking the Docker version either on a Windows Command Prompt or an macOS/Linux Terminal application by running a command like this:
Here I have Docker version 18 installed.
