I previously used the standard mileage deduction in the first year, and now want to switch to the actual expenses method, but Turbotax is not letting me switch.

[DawnC]

Go all the way through the Vehicle Expenses questions.   You will be asked for all of your mileage details (this has to be entered even if you are claiming actual expenses).   Once you enter your mileage details, TurboTax will ask you about your other vehicle expenses.   You will get the option to choose your deduction at the end of the vehicle expense interview.   

Standard Mileage Rate vs. Actual Auto Expenses