To save a file to iCloud:
Upload files Drag files from the desktop or a folder window on your computer to the iCloud Drive window or a folder icon in the iCloud Drive window. If you drag to a folder icon, it becomes highlighted to confirm that the item you're dragging will go into the folder.
How to backup excel files to iCloud on Mac
In iCloud Drive on iCloud.com, do either of the following:
Store your Desktop and Documents folder in iCloud Drive and access them on all your devices. That means you can start a document on your Desktop, then work on it later from your iPhone, iPad, or iPod touch and on iCloud.com. Everything automatically stays up to date everywhere.
How to save PDF document to iCloud Files or another app
First, in the Google Drive app, select the files you want to transfer, follow the steps: Open in > Save to Files > Save. Then go to Files app, find and select the downloaded Google Drive files. Choose organize icon > iCloud Drive. Then these files have been uploaded to iCloud.
You can use that storage space for your iCloud backups, to keep your photos and videos stored in iCloud Photos, and your documents up to date in iCloud Drive. Depending on the size of your backup and amount of content you keep in iCloud, you might run out of free space.
To send a file from iCloud Drive to your Amazon Drive, open up your iCloud Drive on your iPhone or iPad and select the file you want to move. Now tap on the share icon in the bottom left and choose Amazon Drive, then choose where you want to save the file on Amazon Drive and tap "Save" in the bottom right.
A big problem with iCloud Drive's Desktop and Documents Folders synchronization feature is that, by default, iCloud Drive automatically deletes local copies of files when you start running out of storage—by whatever definition of “running out of storage” macOS internally relies upon.
If you keep a local copy of your files in iCloud Drive, they're copied to a folder called iCloud Drive (Archive) in your home folder. You can move any files that were in your iCloud Desktop and Documents to your new local Desktop and Documents.”
Use Finder to View iCloud Drive on a Mac Finder is the best way to find and manage any files on your Mac or in your iCloud Drive storage. You can even combine the two by enabling the Desktop & Documents Folders option in your iCloud Drive settings, to sync those folders from your Mac to iCloud.