How do i change apple ID?

Howdy,

Please see Change your Apple ID

1. Go to appleid.apple.com and sign in.
2. In the Account section, choose Edit.
3. Choose Change Apple ID.
4. Enter the email address that you want to use. 
5. Choose Continue.
6. If you changed your Apple ID to a third-party email address, check your email for a verification code, then enter the code. Learn what to do if you didn't get the email.
7. If you use services like iCloud or Messages to share with friends and colleagues, sign in to those services with your updated Apple ID.

or Change your Apple ID email, password, or profile picture

Then What to do after you change your Apple ID or password

ivan