There are two different ways of getting HIDs that are being posted in this thread. Some people took the lights off of other cars such as the IS 300, they modified the integra head light assembly so that the whole projector assembly for the IS can fit into the integra head light..
Schmoo has a kit where the HID bulb fits directly into the stock integra headlight assembly and just needs to mount a balast (the box that holds all the electronics for the HID system) for each light somewhere in the engine bay.