The easiest way to find out which wire is hot when the parking lights are on is to use a multitester or light probe. This can be used if trying to find out which wire from the headlight plug. If you just go to the parking light bulb, and tap on to the wire that is not black or brown, that would be the one that will provide +12 volts when turned on. I would wire in a 12 volt relay between the power and the lights, it takes a lot of the stress off fuses.
The relay will have 4 wires attached to it. 1. ground, 2. constant power/accessory power 3. wire to lights 4. wire from parking light plug.
If you have any more questions, plz ask, I can try to go into more detail.