If you want to make changes to your 2018 tax return you need to follow the same steps as if you are going to amend your 2018 return.
To download the software and .2018 Tax File you need to go to Documents on the left hand side of TurboTax.
Download the software to your computer.
Download the .2018 tax file
Open the software
Find a Tax File (.2018 Tax file)
Open your return and make any changes necessary.
To file your 2018 tax return you will need to print, sign, date and mail it according to the instructions that print out with the return.