How do I change my Apple ID to a different email address?
How can I change my Apple ID to my gmail address?
iPhone 8 Plus
How can I change my Apple ID to my gmail address?
iPhone 8 Plus
See Change your Apple ID https://support.apple.com/en-us/HT202667.
And see What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071
(supplementary to what the fist link says)
Note that you will not be able to change to your gmail address if your current Apple ID ends in mac.com, me.com, or iCloud.com.
See Change your Apple ID https://support.apple.com/en-us/HT202667.
And see What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071
(supplementary to what the fist link says)
Note that you will not be able to change to your gmail address if your current Apple ID ends in mac.com, me.com, or iCloud.com.
If you change your Apple ID, then anything you have gotten from the Online Stores will not transfer to the new Apple ID. You will need to repurchase and re-download it all.
For Problems With Your Apple ID
Reset Security Questions
Contact Apple for help with Apple ID account security
If you forgot the answers to your Apple ID security questions - Apple Support
You may need to reach Apple’s Account Security department. If you cannot find your country or are not able to call, then complete this form and send it to them.
Try using Apple's iForgot service. If it says they don't have sufficient information, you need to contact Apple's Account Security team. To reach them, click here and pick a method; if you can't use any of the ones listed, fill out and submit this form.
How do I change my Apple ID to a different email address?