If not, its pretty straight forward.
The correct way to do it is to splice a wire into the high beam lead to a headlight and run it back into the cabin to a simple on/off switch.
The other side of the switch runs back to a standard automotive relay to one side of the coil. The other side of the coil is run to earth (the body).
Then the relay will have two normally open contacts, one side runs to the positive side of the battery via a correctly sized fuse for the lights, the other side runs to the positive lead for the lights. If the lights have s second wire this runs to earth (the body), some lights have an internal connection for the other connection.
Didnt have a diagram on me so I googled and found this: