If you’re struggling to try to get your iCloud account with multi-factor authentication enabled to work properly within Outlook, and you’ve tried going to File > Account Settings and tried changing your password there, you’re in luck.
You first have to generate an app password at appleid.apple.com.
Next, you have to go through Control Panel, Mail app and then choose the iCloud account there. Next, click on change and then enter in your newly created app password. Click next and allow it to do a test send/receive. If it sends/receives OK then go ahead and click finish.