If you efiled there should be an Electronic Postmark page saying when you filed and when the IRS accepted it. Probably near the end. That is your proof and signature. If you print out your return to give someone you will have to sign it in ink for them now.
How to get or print a copy after filing, Save the PDF
https://ttlc.intuit.com/community/saving/help/how-do-i-save-my-turbotax-online-return-as-a-pdf/00/26...
