Start by clicking “Save”. This reduces the complexity a bit. Save it in “My Documents” or a similar place.
Now you have a file in the file system, and you can try to open it with double-click, or more appropriately, right-click it and select AxCrypt | Decrypt. I don’t think Turbotax actually opens files by double-clicking, so you may have to import it or otherwise get it “into” Turbotax.