You can't enter a money figure, but you can enter number of miles. If you just have a money figure, divide it by cents per mile (.545/mile):
1. Click Federal
on the left-hand side menu.
2. Click Deductions
& Credits across the top.
3. Scroll
down to Medical and click Show more.
4. Click Start
or Revisit by Medical Expenses.
Click
Continue to get through the list (I did seven times) till you get to the screen below: