To file a return for a prior tax year
If you need to prepare a return for 2015, 2016, or 2017 you can purchase and download desktop software to do it, then print, sign, and mail the return(s)
https://turbotax.intuit.com/personal-taxes/past-years-products/
Remember to prepare your state return as well—if you live in a state that has a state income tax.
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 received the return.
Note: The desktop software you need to prepare the prior year return must be installed/downloaded to a full PC or Mac. It cannot be used on a mobile device.
where can I find the information to download to my computer?
What information? I gave you the link to purchase the software you need. Obtaining your income information, etc. is up to you. If you need to contact old employers, etc. to get copies of W-2's, etc. get busy and do that.
You may be able to get "some" of your income information from the IRS by requesting a wage and income transcript. That will show what past employers reported to the IRS.
It will not show the actual W-2, 1099’s, etc, but will show the income information the IRS received. It will not, however, show your state information. It will only show the federal information.
<a rel="nofollow" target="_blank" href="https://www.irs.gov/individuals/get-transcript">https://www.irs.gov/individuals/get-transcript</a>
For a fee of $86 you can also get copies of W-2's from Social Security:
To get a copy of a W-2 from Social Security <a rel="nofollow" target="_blank" href="https://faq.ssa.gov/en-us/Topic/article/KA-02501">https://faq.ssa.gov/en-us/Topic/article/KA-02501</a>
<a rel="nofollow" target="_blank" href="https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-answers/irs-procedures/transcript-or-copy-of-form-w-2/transcript-or-copy-of-form-w-2">https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-answers/irs-procedures/transcript-or-copy-of-form-w-2/transcript-or-copy-of-form-w-2</a>