When you were entering your 1099-B, it would have asked you how you wanted to enter sales and the options were a) one by one or b) Sales Section totals.
If you selected Sales Section Totals, then you cannot enter the date acquired and instead you would add information based on Short Term and Long Term Gains and Losses.
However, if you select the option of one by one, then you will be able to enter the Box 1b Date Acquired information on the next screen.
If you want to edit the information once you have entered it, you will go to Wages & Income section and you should see the information you have entered under the "Stocks, Cryptocurrency, Mutual Funds, Bonds, Other" Entry on top. Click on Review next to it and then click on Review again on the next screen and you would be able to edit the information you have entered previously.