If you have not filed it you do not amend. You just continue and make your changes and print and mail it. You will need to switch to the Desktop installed program.
If you paid for the Online version ask support to give you the Desktop program download.
https://support.turbotax.intuit.com/contact/
How to finish a prior year online return
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...
You will first need to download the tax data file from Online. It will end in .tax2022, .tax2021, .tax2020. You can download the tax file for free. Then you need to install the Desktop program.
After you get the program installed the first thing to do before you open your tax return .tax file is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW).
If you didn't pay for the Online version you will have to buy the Desktop program download. You can buy the last 3 years of Turbo Tax here,
https://turbotax.intuit.com/personal-taxes/past-years-products/
