If you are using CD/Download version proceed as follows.
Open form 1040 in Forms Mode.
Click on the dollar amount of your IRA or 401k.
A magnifying glass will appear. Click on that.
This will take you to a Worksheet.
Look for the tiny "Explain" button. Click on that.
the form will open.
To explain, just tell IRS what you did, briefly.
Include dates and amounts.
Note: instructions based on TurboTax 2018. It should still be the same in 2020.