How do you navigate the website so I can file for previous tax example 2020 2021 2019

[mesquitebean]

You can't prepare 2019 and 2020 returns online with TurboTax.  Only a 2021 return can currently be prepared in Online TurboTax.  Tax years 2019 and 2020 would have to be prepared in desktop software for each particular year.

You can purchase 2019 and 2020 desktop software programs directly from TurboTax as downloads at this page and install each one on your computer:
https://turbotax.intuit.com/personal-taxes/past-years-products/

Or you may be able to find the 2019 and 2020 software cheaper at a reputable authorized retailer like Amazon, but even there be sure it is a legitimate authorized product from Intuit sold directly by Amazon itself, since there's no way to be sure all third-party sellers on Amazon are legitimate.  

NOTE:  Be aware there are "too-good-to-be true" Internet scam sites selling fake or pirated software. 

Minimum system requirements for Windows version:
https://ttlc.intuit.com/questions/1901571-minimum-system-requirements-for-turbotax-windows-software

Minimum system requirements for Mac version:
https://ttlc.intuit.com/questions/1899173-minimum-system-requirements-for-turbotax-mac-software

The 2019 and 2020 returns cannot be efiled.  Each one will need to be printed, signed, dated, and mailed.  It's a good idea to mail by a method that has tracking, such as certified mail, priority mail, etc.  And you should mail the returns for the different tax years separately in different envelopes.   Do not combine returns for different years in the same envelope.

If you have both Federal and state returns, you need to mail each Federal return to the IRS, and each state return (if applicable) to the state tax agency.

[mesquitebean]

I typed "2029" above in one place instead of "2019" but have now corrected that obvious typo.   However, you may have been emailed the answer with the typo.  Sorry about that.

TIP:  If you prepare the 2019 return first, then you can transfer the *.tax2019 data file into the 2020 return.  Then once the 2020 return is completed, you can transfer the *.tax2020 data file into your 2021 return.   This is important if you have any carryover items from year to year, such as capital loss carryover, foreign tax credit carryover, depreciation items, etc.