After you file

If your return has been Filed and Accepted, at the Sign In page of TurboTax, click the arrow next to 'Show' to the right of 'My Tax Returns and Documents' (screenshot). 

Choose Download.  Once you have the PDF file of your return, look for a worksheet called 'W-2 and W-2G Summary'. 

You will be able to see your Box 12 entry.