In order to connect to a classroom projector and speakers you will use the HDMI cable found on the front desk.
Plug this into the HDMI port on the left side of your notebook
Should you find that your sound is not coming through classroom speakers, check your default sound playback device. See here for more help
Once you are connected to the projector via HDMI use the 'Win+P', projection mode keyboard shortcut, to either extend or duplicate your laptop screen. See here for more help
If you find your screen is turning off and going black (timing out) too quickly you can change a setting in power options to extend the time. See here for more help.