This is what Turbotax help told me to do.
"First, make sure you really need to amend and that your 2017 return was accepted (or paper-filed) in TurboTax Online. You can't amend a return that hasn't been filed yet. More info
1. Sign in to TurboTax and make sure you've selected Tax Home on the left side of your screen.
o If you don't see this, select the menu icon in the upper-left corner to expand the menu.
2. Under Your tax returns & documents, select Amend (change) 2017 return.
o If you only see the option to amend 2016 or earlier, it's because you can't amend an unfiled 2017 return. Select Take me to my return, make your changes, and disregard the rest of these instructions.
3. Carefully follow the onscreen instructions and don't worry if your refund changes to $0. This is normal on amended returns.
4. When finished, we'll give you instructions for printing and mailing your amended return, as amendments cannot be e-filed.
Three weeks after mailing your amended return, you can start tracking it at the IRS Where's My Amended Return? tracking tool. Please allow at least 16 weeks for the IRS to process your amended return."
