The following command will download and run Keycloak's docker image in your local environment (The latest supported version is 8.0.1). It will also create an Admin user with the username and password that you specify in the command, please choose a secure one.
docker run --name "keycloak" -e KEYCLOAK_USER=your-username -e KEYCLOAK_PASSWORD=your-super-secure-password -p 8080:8080 jboss/keycloak:8.0.1
Once Keycloak finishes loading, it will be available on this URL http://localhost:8080
Click on Administration Console and log in with the Admin user that you created at the docker run step just above. It will bring you to the master Realm