The form for entering the distribution is not available in TurboTax yet. The IRS just released the form a couple of days ago. It is Form 8915-F. It should be available in TurboTax soon, but they have not given a date.
When the form is available you will enter the income in the retirement section. If you did not receive any 1099-R for 2021 you will say that you did not receive a 1099-R. Then it will ask about a 2020 withdrawal that you chose to spread over three years.
