I have printed my return for mailing, but have not mailed it. How can I reopen the return to add a document I just received? I would then like to print it for mailing

To access your current or prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state. 

This will take you back to the 2021 online tax return where you can make any changes needed on the tax return.