How to use iCloud Drive on iPhone and iPad? On the following screenshot from https://www.apple.com/icloud/icloud-drive/, it looks like I can use an iCloud app on iPhone and iPad.  But some webpage such as http://www.imore.com/how-set-and-use-icloud-drive-iphone-and-ipad says that there is no iCloud Drive app.

I hunted every where on the iPhone 5S and iPad Air which both have iOS 8 and has iCloud enabled, but I can't find such screen as in the screenshot below.

So how do I go to the screenshot as below?  I upload a PDF file, a picture, and an mp4 file on my Macbook using the Chrome browser on www.icloud.com, but can't access those files just like how I would use DropBox or Copy (which has 15GB free).
Those screenshots are from inside Pages, an app which contains support for iCloud Drive and allows you to select any Pages file inside any of your folders in iCloud Drive.

You can't just 'access' the files in iCloud Drive in iOS like you can on Dropbox. You need to use an app which supports that filetype and iCloud Drive to be able to open the files.