W-2 statements from previous years should not be included in your current year's return. Since it is 2018, the only W-2's that should be included are those dated "2018" on the W-2 form.
W-2's for other years belong with the returns for those years. (2017 or 2016, for instance.) If old employers remain on the list of W-2's in your return, you may delete them from your return, by choosing "Federal" in the left bar, then "Wages & Income" and "Job/W-2." Click the trash can icon next to the W-2's you no longer need to report.