This article explains how to set up a projector and laptop for presentations.

If the laptop is connected to the projector with audio/video cables, do the following:

Make sure both the laptop and the projector are turned off before making any connections.

You can turn off a laptop by pressing the power button or by using the shutdown function in the operating system. To turn off a projector, press the power button, usually on the top or front of the device; if you can't find it, simply unplug the power cord.