For the digital scene you probably aren't looking to have students pair programming. The pair programming feature is meant to allow two students to work on one computer, one person is the driver (controls the computer) while the other person is the navigator (tells the driver what to do), and both students get credit for completing the puzzles.
For the design a digital scene project you want students to work individually on their part of the project and then share their work with each other. This can be done using the share button at the top of the screen in app lab.
Hope that helps!