Your W2 should have, by law, been sent to you by Jan. 31, 2013. If you don't have it yet, as another said, call your employer. The Social Security Administration should have sent you your W2, or retirement earnings if any, by Jan. 31. IF not, call them.
They get it when you send it in with whatever tax form you send in. Now if you are asking when you are suppose to get your W2 you should have gotten it by now. If you haven't contact our employer and have them send you another one.