If you are using a MAC, you will need the adaptor that came with the laptop.
NEC Remote (left) & Sony Remote (right)
On a PC, you will have to select the display by Pressing at the same time the FN (function key) and the F5 or F7 or F8 key depending on which Model you are using (whichever is labeled LCD/CRT or has the icon of a display). Wait to see if the display comes on the laptop and screen. If not, repeat this step.
Repeat: Press RGB 1 or RGB2 if using the NEC remote. If using the SONY rempoe, press the INPUT button until you see the image.