Yes, you can. However, it will not be easy. You will first have to recreate your original return in TurboTax as if you have never filed. It has to be prepared exactly as it was originally. The same applies if you also need to amend state return.
Only then, you can go to the amendment option and amend the original return. I would also recommend that you buy cd/download and not do it online.
Once you recreate the original return, here are instructions on how to amend return: (they are given as if you have prepared with TurboTax, which is what will apply to you, once you recreate it): (use the images after you create your original return).
https://ttlc.intuit.com/replies/3288565
