How do you sing for your taxes

you don't actually sign the return unless you are mailing it in.  for e-filing the prior year's adjusted gross income serves in lieu of a signature. 

Ok so I don't need to sing the page that says to sing it cause when I do it says says it doesn't match what you guys have

I am so confused one person says I don't have to but then I can't go further into filling I just want to get my taxes done and get my money.Im not getting strat answers