I need to file 2018 taxes how do them?

Oh---good thing you did not e-file since the online software is ONLY for a 2019 return, and e-filing it with 2018 information would be a mess.  First you need to clear out the entries and ret rid of that 2018 data that you entered in to the wrong program.   Later you can come back and use the online program to enter your 2019 data.

https://ttlc.intuit.com/questions/2586254-how-do-i-clear-and-start-over

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.