Sorry you can't use online. Online is only for 2019.
To do a prior year return you have to buy the Desktop program here, https://turbotax.intuit.com/personal-taxes/past-years-products/2017 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...
Or If you have a simple return You can fill out the blank forms for free.
Here are some blank forms & instructions for 2017
1040 https://www.irs.gov/pub/irs-prior/f1040--2017.pdf
Instructions https://www.irs.gov/pub/irs-prior/i1040gi--2017.pdf
1040A https://www.irs.gov/pub/irs-prior/f1040a--2017.pdf
Instructions https://www.irs.gov/pub/irs-prior/i1040a--2017.pdf
1040EZ https://www.irs.gov/pub/irs-prior/f1040ez--2017.pdf
Instructions https://www.irs.gov/pub/irs-prior/i1040ez--2017.pdf
2017 Tax Tables https://www.irs.gov/pub/irs-prior/i1040tt--2017.pdf
Publication 17 Tax Guide for 2017 https://www.irs.gov/pub/irs-prior/p17--2017.pdf
Don’t forget your state. And you will have to print and mail your returns. So be sure to attach copies of your W2s and any 1099s that have withholding on them. 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.
