Get your taxes done using TurboTax

When you go to the investment sale entry screens in TurboTax you should see the option to enter sales "one by one" :

When you choose that option, you will have the ability to indicate that you are entering ESPP stock and TurboTax will walk you through entering in the correct cost basis:

You enter investment sales in the Wages and Income section of TurboTax, then Investments Sales, then Stocks, cryptocurrency, Mutual Funds, Bonds, etc... Skip the section where it asks if you want to upload your tax documents.