How do I go back and put me electronic signature

What are you doing and why??

If you already filed, you signed electronically on a screen that asked you to choose a 5-digit PIN (you choose the digits), today's date, and your birth date.

When I look at the printed copy of my return my name isn’t in the signature box, I did see where someone else explained almost the same answer as you. I was just making sure I didn’t leave it off. 

When efiling, there is not going to be any signature showing on the paper copy.   If someone asks for a signed copy of your paper return, you can always manually sign it for them then.

In your complete PDF of your return (the one with the worksheets), there should be a page called "Electronic Postmark" that shows that you filed electronically and when it was accepted, etc.

Here's how to get the full PDF with all the worksheets by opening the return and going to the Print Center:

NOTE:  When you open your return back up, do not make any changes in it if it's already been filed.  If you later have to amend the return, it has to start off exactly as it was when it was originally filed.

• Log in and at the Tax Home or in the section "Your Tax Returns & Documents" for 2019, look for a link "Add a State."
• Click on "Add a State."  (you don't really add one.  That's just to open your return back up.)
• After the return is open, click in the left menu column on TAX TOOLS, then PRINT CENTER.
• Then choose "Print, save, view this year's return."
• The next screen should offer some options:  "Just my tax returns", or "include government worksheets (optional)", or "include government and TurboTax worksheets (optional.)"
• The latter option has the most pages.

NOTE:  Remember all PDF tax documents and tax data files are very sensitive files, since they contain your personal ID info, financial data, and possibly bank account numbers, etc.  Be sure to store them safely and securely to guard against computer theft, hacking, etc.