Cable clip question

With all the pics on this site, I just might figure out which cable goes to which actuator rod. My 68' shop manual shows the defrost cable bracket to the left of the dual vent tubes, mine is on the right facing the box in the same direction. For now, my question is, how to pop the cable clamps on to the bracket. I figured out the tab goes in the big hole, but how to snap the top over the bracket? Also, someone told me a small screw goes through the tiny hole at the top of the clip and bracket. There were no screws on mine when I took it out. If true, what size would they be? Why is it always this small stuff that throws a monkey wrench in everything?