Fog Lights Retrofit VW Golf 4

Hello!
I want to retrofit fog lights onto my Golf 4. I've already purchased the headlights with fog light housings. However, unfortunately, the wiring harness for the fog lights is not standard equipment in the car. This means that I have to install all the cables myself. I've heard that a relay also needs to be installed somewhere in between. Has anyone here done such a conversion before and can help me?
I would like to know exactly what needs to be done and what should be considered.
Sure, no problem! Just provide the text you want me to translate.

Regards,
Thomas.