Yeah, you need more information here. What happens? Is it a new PS3?
Try changing the input. Sometimes the display is set to HDMI and you won't see anything unless you use the yellow, white and red RCA plugs and change it in settings.
If you can't see, which would be the situation here, hold the power button, IN THE FRONT, not the back, and it resets the input mode. However, it resets back to RCA.
What issue are you having though? There are plenty of people willing to help and have the knowledge to do it. Let us know.