This video will walk you through the steps of installing a Linux distro inside a virtual machine.  I have chosen Fedora 24 for this tutorial because this particular distro can be setup to resemble a Mac computer, and that seemed fitting for a VirtualBox machine on Mac.

VirtualBox can be downloaded hhere:
https://www.virtualbox.org/wiki/Downloads

Fedora can be downloaded here:
https://getfedora.org/

Switched To Linux is not affiliated or compensated by either Oracle or Fedora