You'll enter any out-of-pocket medical expenses by clicking on the Federal Taxes tab, then Deductions & Credits, then scroll down to Medical and select Medical Expenses. Then follow the prompts.
If you've already entered all your income information, then TurboTax may ask you how much in total medical expenses you have (before taking you to the input screen). If so, it's doing this to save you the work of entering expenses that won't contribute to your bottom line, since medical expenses are subject to a limitation based on your adjusted gross income. If you see this screen with a pre-calculated amount, that's why TurboTax is asking you the question.
