you don't want to add the lights onto the headlight circuit, its not designed for that much amperage,
So what you'll want to do is get yourself a relay with a harness, the 30 amp kind, it will have terminals such as 87,87a 30, 86 and 85,
you'll wire the 30 directly to the positive on the battery terminal,
87 which is normally open to the lights positive, ground the lights wherever,
then ground terminal 85 also, and then 86 will be your signal wire, when it gets a positive 12 the relay will be energized and voila you'll have light !
so determine which wire is hot in the headlight harness on highbeam and splice into that, only downside to this method is that you have to tap into the vehicles harness, seal everything up and you wont have any corrosion issues,