Go to appleid.apple.com and sign in
Select Sign-In and Security
Select Apple ID or Email Address
Enter your new email address
Follow the verification steps sent to the new email
Enter the verification code if prompted
Sign in again with the new Apple ID email on your devices
Update your Apple ID email in Settings on iPhone, iPad, or Mac if needed
If you use a third-party email address, make sure it is not already used as another Apple ID
If you cannot change it online, contact Apple Support