That depends on the type of income/business you client has. See this article for more info. Even though the layout of these screens may have changed somewhat this year, this article is still a good reference.
Still an AllStar
You don't "enter the deduction" because the software calculates it. You enter the income.
Schedule C at the bottom of the w/s has info needed.
Schedule E and K-1s also need input to get QBI.