The user interface and App Store description gives you the impression that this app would work like the upcoming iCloud Drive app (on iOS 9). It does not.
It can download files that you have selected from iCloud Drive, and thats about it. You can also upload files to iCloud Drive. These things are manually; the app does not just show the contents of the whole iCloud Drive.
It would have been very easy for the developer to clarify this in the App Store description or also within the app. Because this is a paid app that does not work as advertised i will rate it with one star.
elev364ft about Cloud Opener - File manager, v2.0.2