To install on the Windows 8 PC, I used a product key given to me by Microsoft for pre-release testing, otherwise you would have to go to Office.com to buy a subscription and get a product key. (A free 30-day trial is available.) The Windows 8 PC install took about 20 minutes, and a helpful introduction walked me through key points of Office 365.
According to Daily Tech, you can get around that pesky requirement to have Windows XP or Windows 2000 already installed on your PC by instead using the upgrade DVD to first install a 30-day trial version of Vista --that's done simply by not entering the product key when prompted to do so during the installation.