How do I use my 2019 AGI to file for this 2020 year? I am not given/do not see the option to insert my 2019 AGI. (I believe this to be beneficial for me given Covid19)

Using your 2019 Adjusted Gross Income on your 2020 tax return isn't part of the tax relief options available when filing your 2020 return.  You're probably referring to the ability to use your 2019 earned income to compute your 2020 earned income credit and/or additional child tax credit.

See Other taxpayer relief on page 6 of the Instructions for Forms 1040 and 1040-SR for more information.

The TurboTax program will determine whether you're eligible to receive either of these credits by your interview responses.  If you're eligible, you'll be given the option to use your 2019 earned income for their computations.