Amending Prior Year that was prepared by CPA

Yes, you can purchase TurboTax for 2021 and amend a return that was not done originally in TurboTax. 

As Bsch4477 points out, you would have to reproduce your return in TurboTax before you amend it. 

The first step is to purchase TurboTax and install it on your computer. Click here to make your purchase. 

1. Next, you need to enter all of your 2021 information that was on the first return and make sure the return matches the one that was filed. You can click on the Forms icon in the upper right corner to see the 1040, or you can print it. 
2. Compare each line of both pages of the 1040 to make sure everything matches. 
3. Save your return.
4. Click on File in the upper left corner and Open return. 
5. Under Need to File an Amended Return?, select Amend a Filed Return.
6. Select Amend for the return you need to amend
7. On the We’ll help you change (amend) your return screen, select Continue. 
8. Select Yes, I’ve already filed my return.
9. Choose the option that best applies when asked Tell us a little more about your amend situation and Continue.
10. On the next screen, select Update next to the info you need to change
11. Continue through the screens, make the changes you need to make, and carefully answer the remaining questions to finish amending your return
12. Don’t forget to select Save As (or Duplicate on Mac) from the File menu when you save a copy of your amended return. This will preserve the tax return you originally filed. Give the file a different name from the original.