How can I change my apple ID and password?

If you know your current Apple ID and password and want to change the email address that you use for your Apple ID, see: Change your Apple ID - Apple Support

then see: Change your Apple ID password - Apple Support

If you don't know the current one:

If you forgot your Apple ID - Apple Support

or

If you forgot your Apple ID password - Apple Support

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)

Post back if you have questions about what you can do if your Apple ID (1) is a third-party apple ID or (2) ends in icloud.com, me.com, or mac.com.

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Then, change Change your Apple ID password https://support.apple.com/en-us/HT201355 to a strong one (See Security and your Apple ID https://support.apple.com/en-us/HT201303). 

And, once again use What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071