All you have to do is download and install the program from here. Once you sign-in, iCloud Drive will appear in your user folder and in your favorites menu in Windows Explorer.
With iCloud Drive you can directly view and modify files stored in iCloud.
iCloud for Windows also lets you sync with Photo Stream and sync Safari bookmarks with other browsers. If you have Outlook, you can sync iCloud mail, calendars, conteacts, and reminders. However, Windows users are not able to use iCloud Keychain, Notes sync, or Find My iPhone; although you can always sign into iCloud.com to use Find My iPhone and Notes.
Please follow iClarified on Twitter, Facebook, Google+, or RSS to find out more details on Yosemite, iCloud Drive, and when they will be released for Macs.
[via Ars Technica]