You can TRY to use the amendment program and when asked which program you originally used do NOT choose the free version ... instead indicate the SE version and see if you can download it for free ... it has worked for me in the past.   

If this will not work then you will need to either upgrade from the FREE to the SE version which will cost more than you will get for filing  OR  fill in paper forms manually. 

I did not mail the return so it hasn't been filed yet.

it comes up filed in Turbo Tax/  i was supposed to mail it and didn't.  i tried to get back into it on Turbo Tax but it keeps saying it's been filed.  i checked IRS and they don't have it.

If you have not yet mailed the return in then log in & scroll down and click on ADD A STATE to let you back in.