First make sure you're using the same TurboTax account (with the same username) as in prior years. Otherwise, the below instructions won't work.
You can access your prior year returns from the Documents tab in the left menu.
- Select Documents from the left menu.
- Use the drop-down at the top of the screen to choose the tax year you want and then select Download PDF.
If the year you're looking for isn't there, it might be in a different account. Go here to find all of your accounts, one of them should have the return you're looking for.