In order to report the 1099-B, you will need to amend your return with Form 1040X.
Wait until you’ve either received your refund or the IRS has taken payment out of your account. (The IRS will only accept a 1040X, or amended return if your original 1040 was accepted.)
- In TurboTax, scroll down to Your tax returns & documents. Select Show and then select Amend (change) return, and then Amend using TurboTax Online. (If you don't see Your tax returns & documents, select Tax Home on the left.)
- Select the reason you’re amending and follow the instructions.
For further information please see the TurboTax website: How do I amend my 2019 return?