The IRS simply wants to see a Form 1040-X included with the submission of the 2021 Form 8606 when you have already filed your 2021 tax return. The IRS also wants to see an explanation of the recharacterization included with your 2021 tax return, which TurboTax should have already included if you entered the original Roth IRA contribution into TurboTax and indicated that you changed it to a traditional IRA contribution. It won't hurt to include the explanation of the recharacterization again on the Form 1040-X that you will be submitting with the 2021 Form 8606.
Nothing will appear as changes to your originally filed 2021 tax return, so everything in Column B of Form 1040-X will be zero. The only relevant information on the Form 1040-X will be the explanation statement to provide the information mentioned above.
