VT-x should be turned on

Virtualization requires that CPU's virtualization technology has been turned on in BIOS. In Intel x86 platform the virtualization technology is called VT-x. Check either directly from BIOS settings or use software like CPU-Z (Windows only).

Install Docker Toolbox

Docker Toolbox is the recommended installer for OS X and Windows.

• Get started for Linux
• Get started for OS X
• Get started for Windows

Note: Docker Toolbox also would like to install VirtualBox. If you already have VirtualBox installed don't reinstall it but skip VirtualBox installation step.