How to wire these fogs the correct way?

I want to make it so that the fog lights turn on when both the low means and high beams are on, using the headlight switch. I plan on running the turn on lead off the parking light turn on lead. This turns on the parking light from the switch. Do I need to use a relay for anything? I bought one because I thought I needed. But now I am drawing a blank on why.

 

[Buffalosports]

Ok I found a diagram but I am still drawing a blank on why I need a relay.

 

[tonkatruck]

Because the headlight switch and connector have a nasty habit of burning up and/or melting as a result of the increased load of fog lights. Ford engineered very little additional capacity into the headlight switch.

 

[Buffalosports]

Ok, thanks. Also the lights do not dim out. Thats right, sorry.

 

[Sandy]

Ok I found a diagram but I am still drawing a blank on why I need a relay.

This maybe too late but here is my 2 cents.

Yes you need a relay for all additional load.
As state Ford didn't give much extra load capacity to any of its circuits.

You can use the Parking Light Wire to actuate the Fog Light Relay but make use you have an in-line switch.
Also:
1) Use wire gauge appropriate to the wattage of the lamps or larger making sure the lights get all of the current they need. This will let the lights burn at their full brightness and have a longer life.
2) Use an in-line fuse on the main power wire coming from the battery to pin 30 on the relay. This is a safety factor a good idea.
3) Keep the fuse as close to the battery as possible. this will make sure the fuse blow as soon as possible if there is a short.
and
4) Run the ground wire back to the battery or a ground terminal close to the battery.

Luck
OK, #4 is what I do to reduce the number of grounding issues you end up with after a year or two running in wet weather or mudding. It is not a must butit will help to keep the electrons flowing.