How do I attach a windows "csv" file to my amended 2020 tax return

[Critter-3]

It cannot be done ... if you need to attach something you must print, ink sign and mail in the return. 

[fanfare]

If TurboTax won't accept your CSV file, proceed as follows.

Adjust your csv files so the columns are in the same order as on Form 8949.

Put a header with your name tax year and SS Number

before including with your amendment.