You will see a blank projection image, now turn on the computer. When using a laptop computer you may need to disable your computer's display screen. In most cases, to get a matching image, the computer's resolution must match the projector's native resolution. You may have to restart Windows for the changes to take affect. Also note compatible refresh rates, for example 56Hz or 60Hz for SVGA signals, between your computer and projector.
Most projectors can manage a wide range of refresh rates.
Your laptop may have a separate control for external display. In the CRT settings, change the display to either 800x600 or 1024x768 to match the projector. Refer to the projector user guide too see if remote mouse is available. On a Mac, use the ADB cable. In Control Panel, click on Mouse and check the driver.