how to add a device to my account

You mean there is no known data base on how to add a device? Ok so we have a mini it was on the wife's old account took it off. Reset all data in Mini Pad started sign in and it want authentication from cell name that was created by iTunes in a data upload of music. Phone rename to that on the account now the old name is what comes up and no code and codes created from iPhone on account they don't work and we receive notice use code from other apple phone. I have an 11 Pro and there are no codes there. I believe the data base has not been correctly purged and have been unable to manage device to that level as yet. Where is that switch anyway.

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