Open Settings on your iPhone, iPad, or Mac
Tap your name at the top
Scroll down and tap Sign Out
Enter your Apple Account password if prompted
Choose whether to keep a copy of your data on the device
Tap Sign Out again to confirm
Return to Settings and tap Sign in to your iPhone, iPad, or Mac
Enter the new Apple Account email and password
Follow the on-screen verification steps
Update your Apple Account email at appleid.apple.com if you want to change the account email address
If you are changing the account on all devices, repeat the sign-out and sign-in steps on each device