If the Federal section (generally Boxes 1-14) is either identical between them *or* one is blank, enter them as one W-2. First, enter the Federal section; then, enter the state line from each W-2 as a separate line. (Think of it as a single, two-page W-2.)
If they have separate Federal amounts, they're separate W-2s. Enter one, then once you're done you'll be asked if you have any more W-2s to enter; answer "yes" and enter the next one.
