(help) Forgot to file other w2 tax after deadline (april 18)

So, Today is april 18 and the deadline is today. I filed my tax return couple months back and forgot to do my other w2 form. So I Amend my return and added the one i forgot to do TODAY. How Do I know if I have filed it? Do I need to mail? Can i Efile? Do i still get a penalty on 4/18/18? What should i do?