To play a DVD from your MacBook:

Plug in your external DVD drive and use the program, VLC, to play the video and AirPlay to the projector.

If you have not already downloaded VLC, you will see the program available for download from Self Service.

An alternative to using VLC is to use the audio and visual cables in the room to plug into the wall to the projector.

*Note that the goal is to play most movies directly from the Apple TV (See "Showing Movies from Apple TV" help article), but you may need to use a DVD if the video is not available on Apple TV or you are trying to use your existing DVDs.