The Files app is one of the most significant changes in iOS 11. The iCloud Drive app no longer exists and instead we have an app called Files. With this, all of your files will be in one place, files from cloud storage apps such as Dropbox, and from other apps that expose documents such as PDF Expert 6, and even files on your local device. This provides a convenient way to manage all your files in one place and it works on both iPhone and iPad.
How to Get Started With Files App on iOS 11
Open the Files app on your iOS device.
If you are signed in to an iCloud account, you will see all your iCloud Drive files here.
You need to install apps such as Dropbox, OneDrive, and Google Drive to access these services via Files.
Once you install these apps, open Files and hit the Edit button at the top.
Now toggle the switch next to each app whose files you want to see in the iOS 11 Files app.