If, as is in your case, one of your W-2s is mostly blank, just enter the other W-2 and make sure you include the info from the mostly-blank W-2. Usually, "blank" W-2s have additional Box 12 line items or entries for a second state in Boxes 15-20. Don't enter a separate W-2 if Box 1 is empty, as you won't be able to e-file.
If your W-2s are identical down to the last number and letter, you can either keep the duplicate with your tax records or securely destroy it. Don't enter them both.
Otherwise, if each W-2 has different Box 1 amounts which more or less add up to your yearly earnings at that job, enter each W-2 separately. You might get more than one W-2 if your employer switched to a different payroll provider or was taken over by another company, or if you worked at different jobs through the same agency.
