The picture Lee posted is essentially what's in the 1966 assembly manual. Here's a picture from my assembly manual.
The 4 way flashers goes inline with the flasher wiring that comes off the steering column. You need to look for the 2 support bars under the dash that help stabilize the dash/steering column. If you follow the wiring you'll see the existing wiring with those connectors clipped to one of those bars. You basically unplug the connectors and put the 4 way flasher inline. If you need other pics let me know.