You don't show the details of your basis calculation on your tax return. When TurboTax asks for the Adjusted Cost Basis you can just enter the basis that you calculate, including the step-up.
In some versions of TurboTax there is an optional EasyGuide that you can use to calculate the basis. In the EasyGuide you can enter the step-up as an adjustment that increases your basis. In some cases it will ask specifically if you had a spouse who died. It's not clear to me what conditions make it ask that question. But any details that you enter in the EasyGuide are only internal to TurboTax, to guide you through calculating the basis. The only thing that actually appears on your tax return is the final basis amount. You do not have to use the EasyGuide.
