How do I fit a whole new headlight on Citroen Berlingo 2.0 Hdi 2006?

My whole headlight system needs replacing, I have purchased the new full headlight but am having trouble fitting it, I managed to get it in (whilst it was out the indicator was working with the wires plugged in) however when I have put the system in the indicator and full beam are not working whereas the headlamp itself is, there is a purple plug on the van which I cannot see where it is meant to go, im sure it would not be there if it was not required?