You do not enter the Form 5498-SA into TurboTax. If you already entered your HSA contribution from Box 12 of your W-2, you are done with that portion.
If you made HSA contributions not reported on your W-2 (this is uncommon), the TurboTax interview would ask about that when you went through the Medical section. When you were asked the question Were HSA contributions made in 2017? or Do you need to make any adjustments to your HSA contribution amount? and answered Yes there, that would have opened the screen for you to input that information.
Please see below for details on this form.
Where do I enter Form 5498-SA?
