It depends. Are you still working on your return? If so, go back to the investment income section and enter the information from the form you just received. Use Search (magnifying glass) in the TurboTax header, enter "1099-B" and click on the "jump to 1099-B" link.
But if you have already filed your return, you may need to amend and resubmit. If the missing income is significant and would either decrease the tax you owe or increase your refund, you should file an amended return. Note that the IRS is experiencing a major backlog and it may take up to a year for your amended return to be processed.
Should you decide to file an amended return, wait until you either receive your refund or are certain the IRS has accepted and processed your original return.
For more info, see How do I amend my federal tax return for this year?
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