How do you creat another Apple ID on the same phone?

See -> How to create a new Apple ID -> How to create a new Apple ID – Apple Support (UK)

See also -> If you see a Could Not Create Apple ID or Could Not Set Up iCloud message

If you see a Could Not Create Apple ID or Could Not Set Up iCloud message - Apple Support

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What should you do?

If you have another iPhone, iPad, iPod touch, or Mac, you can try setting up iCloud with your Apple ID on that device. Sign in with your Apple ID, then follow the onscreen steps to start using iCloud. 

Or, if you already have an Apple ID set up with iCloud, sign in with that Apple ID instead. 

If you still need to set up iCloud with this Apple ID, contact Apple Support for help. 

Your Apple ID is the account you use to access Apple services like the App Store, Apple Music, iCloud, iMessage, FaceTime, and more. You sign in to all Apple services with this single Apple ID and password.

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You can’t merge multiple Apple ID accounts.

What happens when you use the same Apple ID & Password that you use to sign in here?

See -> Sign in with your Apple ID -> Sign in with your Apple ID - Apple Support