How to sign out of iCloud

That responds to the Apple ID signed in the previous screen to that. Settings ➜ Apple ID.

You would need to scroll all the way to the bottom of the Apple ID page, past the device list, to find the "Sign Out" option, and sign in with whatever other Apple ID you want there.

Do note, you would need to repeat this process on all other devices you wish to be using the new Apple ID.

Also, you would need to change the Apple ID under Settings ➜ Apple ID ➜ Media & Purchases, Settings ➜ Messages ➜ Send & Receive ➜ Apple ID, and Settings ➜ Facetime ➜ Caller ID ➜ Apple ID as suggested by the message your received.

Check Settings ➜ Screen Time ➜ Content & Privacy Restrictions and make sure Account changes are allowed there.

You may need to turn off Screen Time entirely.

The easiest way to deal with this is to remove all of your personal information, sign out and abandon your Apple ID.

Delete it from where exactly?

Or do you mean have it erased from existence entirely?