If you used a paid tax profession for the tax return then it would be best if you used them to amend your tax return. There should be no charge for the amended return.
However, if you choose to use TurboTax then amending return not completed and filed using the TurboTax software is a little complex.
First you will need to purchase, download and install on a personal computer, Win or Mac, one of the TurboTax desktop editions for the year needed (2016 thru 2018) from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
Once installed on your computer you will then have to recreate exactly the tax return that was filed. To include all errors or omissions. Once completed you have to tell the program that you will be printing and mailing the tax return in the File section. This fools the program into believing the tax return was filed so that afterwards you can start to amend the return.
An amended tax return can only be printed, signed, dated and mailed to the IRS or to a State, it cannot be e-filed (except for New York state)
