HOW TO HOOK UP YOUR MACBOOK TO A PROJECTOR VIA HDMI
Here are the required materials:
You should have been provided with an HDMI adapter (aka 'dongle') and an HDMI cable should be in your room.
Plug the HDMI cable into the port next to your whiteboard.
Plug the other end of the HDMI cable into your HDMI dongle.
Plug the dongle into the DisplayPort of your MacBook Pro.
Make sure your projector is turned on. If you see nothing on the whiteboard, push the power button on the projector that looks like this
If all you see is your desktop background, but no windows or icons, you need to Turn On Mirroring.
Click the little icon that looks like a monitor and select Turn On Mirroring. as shown below.