I discovered that I can sign out of iCloud on the Mac and sign in with my correct apple ID. However, I get a message that this alternate ID is not my primary iCloud account ID (whatever that means) and that I need to first remove it from mail, calendars, etc. How do I do that? Will this affect receiving my mail? I don't know.
The bottom line is I don't understand how all this fits together and I can't find any documentation from Apple that explains it.
Am I missing something? Is there documentation somewhere? Did Apple just throw this out for the world to stumble through?