Amending is a special process. You have to start with the original return. So you first have to pretend to do the real return. You can use the Forms Mode to fill it out. It has to match the real filed return including the tax due.
Then save a copy of the first return. Then save another copy with a different name to amend. Go up to File-Save and Save As.
How to amend a Desktop return,
https://ttlc.intuit.com/community/tax-topics/help/how-do-i-amend-my-2019-return-in-the-turbotax-cd-d...
Or You can find Amend under
Federal Taxes or Personal (for Home & Business)
Other Tax Situations
