Cannot display image on a proector using Lenovo...

Question

I cannot display the image on my Lenovo G400 laptop using a projector.
I already tried to press Fn+F8 and even tried other function keys. It didn't work. Tried restarting pc and projector, nothing happens. I also configured the mobility settings on my laptop but the only thing it can display is my desktop wallpaper. What else do I need to do?
Please help. Thank you.