I've downloaded a prior year tax software. How do I launch it from my computer?

Are you on Windows or Mac?  Did you get it installed and activated with the License Code?  How to install

https://ttlc.intuit.com/turbotax-support/en-us/help-article/product-delivery/download-software-turbotax-com/L7u9oLEkq_US_en_US?uid=lxgjjaw0 

Then you just click on the program shortcut Icon on your computer to open it.  It will be a red ball with a checkmark in it.    Here my programs 2016- 2021 on Windows 8.1.  Had to get a Windows 10 laptop for 2022 & 2023.

And....to make sure you know this---your past year return cannot be e-filed.   Past year returns must be filed by mail.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.

Do you need to prepare a prior year return or open a .tax data file you downloaded from the Online version?  If you are trying to open a .tax file there are a couple other steps after you get the program installed and launched.