After you enter the sales information (just enter the description, Number of Shares sold and date sold) the next screen asks how you acquired the stock and whether or not you purchased in one or multiple lots. (see screenshot).  You'll then have the option of choosing to "enter the summary information". If you choose this option, you can enter "various" for "Date Acquired". Then enter for Net Proceeds and Cost Basis along with applicable adjustments, to complete your entry.