How can I store my items in my iCloud so as to free up space

iCloud is not an off-site storage facility. It is a syncing service. You can delete files from your devices which are signed into iCloud but this action will also delete the files from iCloud and all your other devices. See Apple's support document What's the difference between device storage and iCloud storage? (also linked above).

There are ways to manage your iCloud space and this is described in Manage your iCloud storage.

As TheLittles has also recommended - you can buy more iCloud space.

Bakeme Said:

"How can I store my items in my iCloud so as to free up space"

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Upgrade yoru iCloud Storage Plan:

One option (if available in your location, you be to upgrade your iCloud storage plan. Lean more here:

• iCloud+ plans and pricing - Apple Support
• Upgrade to iCloud+ - Apple Support