Help wanted in installing GitLab from Docker Toolbox

I’m trying to get GitLab set up on a 2008 MacPro, running OSX 10.10.5 (Yosemite). I installed Docker Toolbox and used it to try out nginx, etc. However, when I try using the “docker run” command for GitLab, I get:

docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock.
Is the docker daemon running?. See ‘docker run --help’.

See for details.