@blakeviall , if you used desktop version then it is easy --- just open your 2018 TurboTax and tell TurboTax you want to file and amended return and it will walk you through all the steps.
If you used on-line version then , it is difficult because the 2018 on line version is no longer available - you should call customer service on how to get your tax file from 2018 on line , download to your computer, get a copy of 2018 software and then work on amended return as above.
Note that amended returns must be filed by mail to IRS.
If you need more on this , please let me know what I can do for you.
I am assuming here that you are US citizen/Resident ( Green Card ) and have been abroad for more than a year ( which country ? and employed by a foreign entity.
