sign in with an Apple ID
If you use iCloud to store and access mail, photos, and documents, or to use Find My or other services, you must sign in on your device using your Apple ID.
If you’ve ever purchased something from the iTunes Store, App Store, Apple TV app, or Book Store, you have an Apple ID. If you don’t remember your Apple ID, or you don’t have one, click one of the links below the iCloud sign-in fields to either create an Apple ID or retrieve your Apple ID or password.
Do one of the following to sign in:
On a Mac: Choose Apple menu
> System Preferences, then click Sign In and follow the instructions.On an iPhone or iPad: On the Home screen, tap Settings, then tap iCloud.
On the web: Go to iCloud.com.
On a Windows computer: In Windows 7 or later, click the iCloud app or tile on the Start screen, or choose iCloud from the Start menu.
If you forget your Apple ID or its password, you can recover it on the Apple ID website.
If you can’t open a document shared with you by someone else, it’s possible the email address or phone number used to invite you isn’t associated with your Apple ID. Sign in with your Apple ID, then follow the instructions to verify your email address or phone number and associate it with your Apple ID. Afterward, sign in using the primary email address or phone number associated with your Apple ID.
Note: If you don’t want to associate another email address with your Apple ID, you could instead ask the owner of the shared document to invite you again using an email address or phone number that’s already associated with your Apple ID.