3 core wire with earth only 3 attachments in the light? what goes where?

I moved into a house with space for wall lights, i attached the lights, however i had one spare wire from the cable going to the lights and the switch. The light came on but would n't go off i changed the wiring and the switch blew. I've changed the switch, but now nothing works. I've checked the junction box, but it is not tripped. Any ideas, what am i missing???

petelynch
September 2007