The cost basis was not reported for 1 of my stock sales. How do I enter the researched Total Cost Basis?

It depends. If you imported transactions from your financial company, then you will search for the transaction to record the cost basis.  If you want to enter the transaction manually you can do that as well.  Use the instructions below to make your entry.,

• Where do I enter my 1099-B?  
  • -- If you want to enter this transaction manually, then do not choose to import. 
  • --If you already did import and want to add the cost basis scroll your transactions to find the one you want to edit.

If you are using TurboTax Desktop, you can go to Forms, then find your 8949 to enter the cost basis.  From there TurboTax will carry the information for your tax return calculations.