In my new course, I try to help you get the most from iCloud. Here is an excerpt from the first lesson which explains how cloud services work. The course then goes on to show you how to set up iCloud on Mac and iOS. Further videos explain each feature of iCloud such as iCloud Drive, Photos, data syncing, backups, email, sharing and more. You can learn about this and more in the new Guide to iCloud course at https://macmost.com/icloud
If you are using a third-party email address as your Apple ID, you may need to change it if you are losing that email address or plan to move on to another email service. Apple has a page that spells out the steps needed to change which email address is used as your Apple ID.