virtualbox.org

I downloaded the VirtualBox but I get "no bootable medium found! system halted". I HAVE read all the posts under this topic, also followed the link to understand what a "virtual box" is, also read the manual. But the language is beyond me (ISO? host disk?) and I don't know how to proceed.
Can anyone give me simple but clear instructions to a neophyte so I can resolve this?
Thanks,
Chris

VirtualBox is a PC in Software, not an OS. You must install an OS.

How do I do this?
Chris

I have an OS on mac (Lion) and I understand that I have to install a OS from windows so windows can run within my mac, but I can't fathom how do this. I read about "selecting the small folder icon next to drop down disk etc" but all of the choices were like Greek to me. I'm stymied.

Read the VirtualBox FAQ, which has a link that describes what a Virtual Machine is.

I'm going to lock this thread, because there is no beta going on now.