The W-2c is the "corrected" W-2 form. So you can ignore the W-2 and
input only the W-2c, since that takes precedence. You'll enter it on the
same W-2 screen that you would enter a regular W-2.
Once you've entered the W-2c, you'll be shown a screen with a list of uncommon situations, where you'll check the box for corrected W-2.
