If you have filed your 2015 tax return and it has been accepted by the IRS, you will need to file an amended return to correct the 1099-B and 1099-DIV information. TurboTax will guide you through correctly entering your new data and printing Form 1040X. You may also have to amend your state income tax return if you have a state income tax. Please note that amended tax returns must be filed by mail.
For more information, please see TurboTax Guide - Amending Your Income Tax Return.