If your Itemized Deductions exceed the Standard Deduction allowed for your filing status on your Oregon state return, TurboTax should automatically apply the Itemized Deduction on your return because it brings you the most tax benefit.
You can view which deduction you are taking by clicking on Forms in the upper right-hand corner and then looking for your OR-40 on the menu on the left. Your deductions will be on Line 16 or Line 17.