How do i file my 2018 & 2019 taxes? i did not file last year oso i wanted to do them both now

That will be TWO separate returns.  Each year has to be filed separately.  Do not try to combine them.  The online software is only for 2019---no other year.   Only a 2019 return can be e-filed.  Since you have not filed a 2018 return you will have to try using "zero" as the 2018 AGI in order to e-file 2019.  Even if you prepare 2018 first, the AGI on the return will not be in the IRS system so do not try to use it.

Online preparation and e-filing for 2018 is permanently closed.

To file a return for a prior tax year

If you need to prepare a return for 2016, 2017, or 2018 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/state 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.

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.

https://ttlc.intuit.com/questions/1900990-how-do-i-file-a-prior-year-tax-return