Here are the two guides that helped me get the install done. Just install VirtualBox, then follow either one of these guides. The video is more up to date, but the text version is not much different.
http://askubuntu.com/questions/142549/how-to-install-ubuntu-on-virtualbox
Once you have ubuntu going, head on over to Joseph's guide here ...
https://steemit.com/steemhelp/@joseph/mining-steem-for-dummies