Where do I located the "adjust cost basis" field. The help screen shows it is an option. I cannot find the section.

Are you referring to an entry for an IRS form 1099-B transaction?  Or something else?

 

For the entry of IRS form 1099-B stock transactions, you may select The cost basis is incorrect or missing on my 1099-B.

 

 

At the screen We noticed there's an issue with your cost basis..., enter the adjustment.