Are you using a laptop or the installed computer?
If you are using a laptop try this:
1) Leave your laptop turned OFF.
2) Connect either the VGA or HDMI cable.
3) PRESS “ON” on the projector control panel.
4) Now turn on your laptop. (Turning on in this order gives the laptop/projector the best chance of “handshaking.”)
5) You will probably see your laptop screen flash off & then on again. Also the resolution on your laptop screen may change to match the projector resolution. Be patient during this process & don’t disconnect the laptop or try to change the settings.
6) If you are using an Apple computer, occasionally the screen will not automatically re-size correctly. You can go into the Display settings to re-size the laptop screen and the projector image manually. Another trick is to reboot the Mac laptop while it is connected & the projector is on. Sometimes that process will force it into the correct resolution.
7) If you are turning on the projector & then “hot plugging” the laptop while it is on, the screen resolution may not resolve correctly.