I have installed many systems and you can either use a 4x4 electrical box mounted to the beam with beem clamps a piece of counduit and another 4x4 box at the base then install the camera to that or a flange plate with a 1 1/2 inch threaded pipe then the dome mounts to the threaded end at the base. It all depends on the weight. You can pick most of the stuff up at Home Depot eccept the domes.
Mike