How do I prepare or enter form 8606 details? I had to recharacterize a 2020 Roth IRA contribution to a regular IRA.

You will enter the recharacterization when you enter the contribution to the Roth IRA

1. Login to your TurboTax Account 
2. Click on "Search" on the top right and type “IRA contributions”
3. Click on “Jump to IRA contributions"
4. Select “Roth IRA”
5. Answer “No” to “Is This a Repayment of a Retirement Distribution
6. Enter the Roth contribution amount 
7. Answer “Yes” to the recharacterized question on the “Did You Change Your Mind?” screen and enter the contribution amount (no earnings or losses)
8. TurboTax will ask for an explanation statement where it should be stated that the original $xxx.xx plus $xxx.xx earnings (or loss) were recharacterized.
9. On the screen "Choose Not to Deduct IRA Contributions" answer "Yes" (if you are thinking about doing a backdoor Roth. If you have a retirement plan at work and are over the income limit it will be nondeductible and you only get a screen saying $0 is deductible)

TurboTax will create Form 8606 for you if the traditional IIRA contribution is nondeductible/you make it nondeductible.