You are probably mixing between letter 6475 Economic Impact Payment (this letter helps EIP recipients determine if they're eligible to claim the Recovery Rebate Credit on their 2021 tax year returns) and letter 6419 which is the official documentation that has the details you need to report your advance Child Tax Credit (CTC) payments.
In TurboTax,The Recovery Rebate Credit will be found in the Federal Review section. You will enter the amount reported on letter 6475.
For the CTC payments, check the link How do I enter my advance Child Tax Credit payments in TurboTax?
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