I purchased the 2020 extension to file and cannot figure out how to access it. I don't see an option in the regular turbo tax where I see the 2021 return.

You cannot file an extension for tax year 2020. 

You can file a 2020 tax return but you will have to purchase and download one of the 2020 desktop editions.  The TurboTax online editions are only for tax year 2021.

To complete and file a 2020 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2020 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/

A 2020 tax return can only be printed and mailed, it cannot be e-filed.

The 2020 extension is immaterial  at this late date so having a copy of it really doesn't matter.  Why do you need it ?