Online is only good for the current year. You can buy the last 3 years of Turbo Tax here,
https://turbotax.intuit.com/personal-taxes/past-years-products/
You will need a full Windows or Mac to install it on.
How to prepare a prior year return
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-prepare-a-prior-year-tax-return/00/25...
You will have to print and mail in prior year returns. And if you are doing more than 1 year, send each year in a separate envelope. Sometimes the IRS will just staple all the sheets together and miss a second return. Be sure to attach copies of your W2s and any 1099s that have withholding on them. Don't forget state. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.
Or if you want to file for free and have a simple return you can get the blank forms from the IRS and fill them in by hand. I have a list of some of the basic ones I can post direct links to. What year do you need?
Here is the link to all the prior year IRS forms
Prior Year Forms and Instructions | Internal Revenue Service
