I struggled with this too as I was close to e-filing when realized I should have used itemized deductions.
This is how I switched from Standard to itemized. I am using the CD version of Turbo Tax Premier.
Click on View on the command bar at the top. You will probably see Step by step checked. Click on Forms. In the Info Wks, scroll down to Part VI. There you can check the type deduction you wish to take. I clicked the box to use itemized and now I see Schedule A in the list of forms on the left side of the screen.
