Actually, in my case (TurboTax Premier), there is no place that says "I'll enter additional info on my own." for 1099-B. That is something I was looking for, since some other forms has it.
Anyway, I was able to do it by selecting "I need to adjust my total cost basis", entering the amount from box 1g and selecting "W (nondeductible loss from a wash sale)".
I don't know why mine is different, perhaps because I selected to enter the summery than all transactions. Anyway, I think TurboTax can make it simple by giving the option to enter what is in box 1g on the first page itself.