If your 2019 federal tax return was e-filed there will not be a signature on the tax return. The 2018 AGI you entered for e-filing the 2019 tax return is your electronic signature and your identity verification for the tax return.
If the loan company requires a paper copy with a signature then print a copy and sign the tax return on page 2 of the Form 1040.
To access your current or prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)
When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state.
This will take you back to the 2019 online tax return.
Click on Tax Tools on the left side of the online program screen. Then click on Print Center. Then click on Print, save or preview this year's return. Choose the option Include government and TurboTax worksheets
If you e-filed your tax return, it did not have a physical signature. The "signature" was electronic. If a lender wants a signed copy, take out a pen and sign on the line that says "Sign Here" on page 2.