model A brake light switch hook up?

[69daytona]

I just bought my first model A, A 1931 coupe with dual side mounts, Car was sitting in a garage since 56 and last registered in 62, Came with all the original parts in good shape plus a new model B engine and Transmission.
I just finished installing the new B engine and trans. and have done just enough wiring to make it run.
The car came with new head light switch and wiring but the problem I have is How to hook up the brake light switch, looks like its mechanical but I cant see how it is hooked up to activate it. Still has the original brake light switch on back side of frame cross member.