Prior to iCloud Drive, your options for Apple's iCloud service were either to use it as a backup service or simply to ignore it. Now with Mac OS X 10.10 Yosemite, iOS 8 and iCloud Drive, you get a proper cloud storage product akin to Dropbox or Google Drive where you can stash and retrieve individual files from any of your Apple devices (there is also an iCloud Drive app for Windows).
Let's have a look at how you go about setting up iCloud Drive on both your Mac running Yosemite and iOS devices running iOS 8.
Pricing
Apple gives you 5GB of iCloud Drive storage for free, and there are four paid plans that provide up to 1TB of storage space for $19.99 a month.
iCloud Drive on Mac OS
On the Mac side, setting up iCloud Drive is easy. When you install Yosemite, you'll be asked if you'd like to upgrade to iCloud Drive. Answer in the affirmative and when you open Finder, you'll see iCloud Drive listed in the Sidebar on the left.
If you didn't enable iCloud Drive when you installed Yosemite, go to System Preferences > iCloud and check the box for iCloud Drive at the top of the list.
When you first open iCloud Drive in Finder, its window will be empty, but you can simply drag files and folders to it to move them off of your Mac and to the cloud. You can also create a new folder by right-clicking in the iCloud Drive window. Your folder hierarchy, however, will be flat; you can add one level of nested sub-folder but no more.
Additionally, iCloud Drive is baked into Apple's iWork apps. So, when you go to save a document in Pages or a presentation in Keynote, for example, iCloud Drive will be listed as one of the save location options. The first time you save a file from an iWork app, a folder will be created for it in iCloud Drive.
From then on, you can select that folder instead of just dumping files into iCloud Drive's main directory. Should you save an iWork file to the main directory, an alias will be placed in the corresponding folder of its app.
iCloud Drive on iOS
On iOS, things are a bit murkier because there is no standalone iCloud Drive app that lets you view all of the files and folders you have stashed in Apple's cloud. Instead, iCloud Drive lurks within Apple's own app and third-party apps. In Pages for example, your list of documents features both those saved locally and those saved to iCloud Drive.
Before you can use iCloud Drive in an app, you have to enable iCloud Drive in Settings of your iOS device. Go to Settings > iCloud and tap on iCloud Drive. Next, tap the toggle switch to enable iCloud Drive. Below the iCloud Drive toggle switch is a list of apps that presumably support iCloud Drive, but I couldn't find any sign of iCloud Drive integration for many of the apps listed on my iPhone.
I'd wager that, after an update, many of these apps will offer iCloud Drive support. I was able, however, to save PDFs to iCloud Drive from Scanner Pro by Readdle.
To move a document that you created on an iWork app on your iPhone or iPad to iCloud Drive, tap the share button in the upper-right corner, choose Send a copy and then select a format.
Next, tap the Send to button and you will see a grid of folders, which represent the apps you have that support iCloud Drive. If an app is not compatible with the file type you are attempting to save, its folder will be grayed out. Tap the folder you'd like (and then a subfolder, if any exist) and tap Export to this location.
For more Yosemite tips, please see CNET How To's guide to Mac OS X 10.10 Yosemite.