Why did you log into your online account? Did you use the wrong instructions? You need to start by opening your original return in the Desktop program. You need to amend the same way that you did the original return in the Desktop program on your computer.
To amend the Desktop program. Start by opening your return as usual. Go up to File-Open.
If you don't see a button for Need to Amend a Filed Return? on your home screen then you can get to it here. Go to:
Federal Taxes -or- Personal (for H&B)
Other Tax Situations
last section, Other Tax Forms
Amend A Return - Click the Start or Update button
How to amend a prior year Desktop return, See the Desktop section instructions
https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-a...