How do you change apple id on an iphone?

Go to icloud.com, sign into your Apple ID and click Find Phone. In the All Devices pulldown menu in the center of the page click on the iPhone and in the dropdown sheet click Erase Phone. Then delete the phone from the account.

The phone should be ready for a new user to set it up with their Apple ID.

ASC - Late 2012 Mac mini, macOS 10.15.5; Watch, series 5 GPS/cellular, watchOS 6.2; iPad Air 2, ipadOS 13.5.1; iPhone 8+, iOS 13.5.1; TV 4th Gen, tvOS 13.4.6;  HomePods, audioOS 13.4.6 and Airport Express w/ Airplay 2

You won't be able to put someone else's on the phone. If you try, you'll find that the other person's Apple ID already is in use. Allowing what you want to do would violate Apple's security protocols.

Or follow the steps in the article below.

Selling/Giving Away Device.