Old photos added to Photos Library on my Mac not uploading /syncing to iCloud
I've recently copied some old photos stored on CD into my 'Photos Library photoslibrary' on my Mac external drive, and I have iCloud Photos ticked under Preferences, but they are not moving onto my iCloud. I have plenty of iCloud space spare. I don't know what else to do. Can anyone please help. Thanks
MacBook Air 13″, macOS 11.5