How do I file taxes from 2017 and 2018?

Sorry---you cannot use TurboTax for those years.  And you are too late to get refunds for any year earlier than 2019.  Earlier year refunds have been forfeited.  If you owe tax the IRS still wants to be paid.

TurboTax has software for 2019 onward.   Software is no longer available from TurboTax for earlier years, nor would it be supported even if you find it on eBay, etc.  Updates are not available.   It is also too late to receive a tax refund for a tax year earlier than 2019---those refunds have been forfeited.   BUT if you owe tax due you still need to pay.

Online preparation and e-filing for 2019 and 2020 and 2021 is permanently closed.

To file a return for a prior tax year

 If you need to prepare a return for 2019, 2020 or 2021 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/

You may also want to explore purchasing the software from various retailers such as Amazon, Costco, Best Buy, Walmart, Sam’s, etc.

Remember to prepare your state return as well—if you live in a state that has a state income tax.

https://ttlc.intuit.com/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/00/25573 

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.

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.

If you are getting a refund, there is not a penalty for filing past the deadline.  If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.

TurboTax does not support tax years 2017 or 2018.

If you are filing these returns for a tax refund, it will not be paid.  It is beyond the 3 year limit for a tax return for a refund from the due date of the tax return.

If you have taxes owed then you need to pay those taxes as soon as possible since penalties and interest will continue to accrue until the IRS receives your tax return and tax payment.

Locate a local tax professional in your area if you have taxes owed to assist you in completing these tax returns.