If you are retired and receive retirement pay, you should have received Form 1099R to include in your return instead of a W-2 unless you worked a job and earned wages also during the year.
If you did not receive your 1099R, then you need to contact your retirement pay office from your last job that you retired from and ask them how to get a copy of the missing 1099R.
If you are unable to reach your retirement office and have a last retirement pay "stub" or report of received income, then you can use Form 4852 as a substitute W-2 or 1099R.
If you do not have the federal ID # of your retirement payer, then you will have to paper file instead of e-filing.