Keynote for Mac: Apple ID
The email address you use to access many Apple resources, including iCloud services.
If you forget which Apple ID you use with iCloud, do any of the following:
On an iOS device with iOS 7 or later installed: On the Home screen, tap Settings > iCloud.
On a Mac with OS X 10.10 or later installed: Choose Apple menu > System Preferences, then click iCloud.
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.
For more information about your Apple ID, visit the Apple ID website.