To amend a return you did somewhere else, you would first have to fill out Turbo Tax like you are doing the original return and pay for it. You have to recreate the actual wrong original return. Then when it matches each line that you really filed you have to tell Turbo Tax you will mail it so it thinks it was filed. Then you can amend it.
For prior years you have to buy the Desktop program. You can only buy the download for prior years. You have to buy a separate program for each year. They only sell the last 3 years. You need a full Windows or Mac computer to install it on. Buy the download here
https://turbotax.intuit.com/personal-taxes/past-years-products/
If you don't have the original Turbo Tax .tax file you have to first recreate the actual wrong original return. You can use the Forms Mode. Then when it matches each line that you really filed you have to tell Turbo Tax you will mail it so it thinks it was filed. Then you can amend it. You will have to print and mail amended returns.