If your HSA contribution is reported in Box 12 of your Form W-2 coded W, you don't need to enter any amount. The amount of your HSA contributions have already been deducted from Box 1 (Wages) on your W-2, so you’re already getting the deduction when you enter your W-2.
But if you made a contribution that isn't reflected on your W-2, you'll need to enter it yourself.
Please see the TurboTax Help article Where do I enter my HSA contribution? for guidance.
