Hello, how do you change email from old to new one

See Change your Apple ID https://support.apple.com/en-us/HT202667. 

And, here is 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 won't be able to change to a 3rd-party Apple ID if you current one end in @mac.com, @me.com, or @iCloud.com.