Re: How can I make sure

I'm under the asumption that your just grounding this outlet. So shut it off and unscrew the device from the box. Make sure there are no bare copper or green wires mounted on the receptacle or screwed to the box. If there are, just leave them alone and buy a isolated ground receptacle (which would be best anyway-but not necessary).
Isolated ground recep have the ground screw isolated from the metal mounting brackets on the receptacle. These have a green isolation symbol on the face. Mount your new ground wire to the green screw on the recptacle. If there isn't any other wires than the white and black (possibly more than one of each) attach your new wire the same way. Most people don't have to worry about all these steps, but if you don't have a grounded system, it's better not to have your computer receptacle the only one. When attaching the new wires look carefully at the back of the device the white wire side will be marked "white". Blacks the other side. Green to ground.