You do not make any entries directly on Form 8949. You can enter the adjustment code and amount on the Capital Asset Sales Worksheet or the Capital Gain (Loss) Adjustments Worksheet. This can only be done in the desktop software, of course, not in TurboTax Online.
I think there used to be a way to enter adjustment codes in the Step-by-Step interview, but I can't find it now in the redesigned interview for investment sales.
