There is no fee to file an amend.
Amend for 2020 will not be available in TurboTax until late March. You do not amend until your original return has been processed. When you start your amend, TurboTax will show your refund amount as zero. Then that amount may change as you amend your entries.
When amend is ready, go into TurboTax and follow the instructions for amend. You will add your dependent in the federal section, then walk through all of the amend questions to be sure the information carries to the state. You will be amending both the federal and the state returns when you add a dependent.
You have 3 years from the date you filed your return or 2 years after you paid the tax due (whichever is later) to file an amendment.
