You cannot import a transcript into your tax return. If you do not have the 2019 tax file to transfer from 2019 to 2020 you will need to enter your data by hand.
An IRS transcript cannot be transferred to a TurboTax tax return.
If you used the TurboTax online editions for tax year 2019 then all you need to do is start the 2020 online return using the exact same User ID you used for the 2019 account.
See this TurboTax support FAQ for how to transfer last year's return to the online editions - https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-...