hi jonesy
I'm assuming you mean how do you remove and replace the old light and get the wiring back through the spoiler?
I think the light is held in by two self tappers. Before you remove the light, tie a piece of string about a metre long onto the end of the wiring. Remove the screws and pull the light away, pulling the wiring through the spoiler until the string comes out the hole. Undo the string, tie the string to the wiring from the new light then gently feed/pull the wiring back through the spoiler.