at the bottom of the entry screen if entering "one-by-one" there is a checkbox "I have other boxes on my 1099‑B to enter" and you can enter 1g there
if entering in summary mode there is a check box "I need to adjust my total cost basis" and you can enter code W
Personally I always use one-by-one for these which will put these items on Form 8949. if you enter adjustments at a summary level it will trigger the need to provide more details to the IRS via Form 8453.
if you have multiple sales (likely) but only some are wash sales you can split up the 1099B, enter the wash sales as one-by-one and the balance of your 1099B you can enter as summary level and it will be consolidated on Schedule D (check the totals add up the original totals for the 1099B).
