It is not clear what you are trying to do. Are you looking for your 2020 or 2021 tax return? If someone else prepared your return using an online TurboTax account then you need the account and user ID to access the account. Or you need to get that person to provide you with a printed copy of your tax return. What AGI are you trying to see? Are you looking for your 2020 AGI or your 2021 AGI?
If you are currently preparing a 2021 return and you are looking for your 2020 AGI so that you can e-file, then you can get a transcript of the 2020 return which will show your 2020 AGI. Or you can just try using zero as your AGI in order to e-file the 2021 return.