First, hot glue the jaws of each bottom skull open.

While that is cooling, take two pig tail light sockets and strip the wire as close as possible and then crimp on the wire connectors.

Self explanatory

Self explanatory

Now you want to center the skulls on the base. Here I used a peace of scrap wood and painted it black.

I then hot glued the skulls in place, and painted black over the glue after it cooled.

For the top skull I removed the jaw and inserted red indicator lights. You can pick these up at RS or most surplus stores. The wiring was run out of the back of the skulls and tied to gather so it would all run off one plug.