@pitreeher did you already file the first one? Was it Accepted? You need to wait and see if your first efile was Accepted or Rejected. If it rejects for something you can fix it and add the missing W2 and resend it. BUT if it is Accepted you have to wait until it is done processing and you get the first refund (or pay the tax due). Which might take a long time. Then you can do an Amended 1040X return to fix it. So do not add or change anything until you know.
