EZ wiring tail light circuitm

I have a 70 Dart and got the EZ wiring 21 circuit harness. I have mounted the fuse box and have all the wires ran. I started at the rear, hooking up lights.

The three wires in the rear are labeled:

1. Left/Right backup
2. Left/Right Turn
3. LEFT/Right Tail Park

My question is how are the taillights grounded? I see three wires in the tail light plugs:

1. Backup: Pink
2. Tail: black
3. Brake: green

Under the dash, there is:

Brake switch power
Brake switch

So I hooked both of those wires to the brake light switch and applied 12V to the power wire and got nothing when I pushed on the brake.

Do the housings need to be mounted? Currently they are not.

Any help would be appreciated.