I'm guessing that you are talking about the big 4 pin adapter. If that's the case, it's not that hard to put them back. I'm assuming here that the metal end is still connected to the wire and you want to put them back in the plastic molex housing...just look closely at the metal pin, you will see some very small fins or slits in the side of the pin. these hold the pin in place. if you didn't break them off, they will likely be bent inward into the pin itself. I would use a striaght pin or safety pin to bend that little fin out a bit so it will catch when you put the pin back in the connector.
Make sure that you put the wires in the right holes...you don't want to short out the board or PSU.