What I do is mix the cure in the water I am adding to the sausage, mix well so the cure is well distributed. Since the meat is ground and the cure is distributed throughout the meat it begins to react immediately, and I stuff it right away. At this point it can go directly in the smoker, but after stuffing you can refrigerate it for several days. I generally place it in the smoker the next day, because by the time I get it stuffed it is pretty late in the day. In addition, while you are drying the sausage, and applying the smoke at low temperatures, this accelerates the chemical reaction of the nitrites. If after adding the salt and cure to the ground meat unstuffed, and you let it cure, even for a little while, the mixture will stiffen and it becomes hard to extrude the meat through the tube when stuffing.
As for the directions on the mix, is it referring to after being stuffed and refrigerated? Prior to being stuffed?
When you freeze any food, it needs to be wrapped, and the better you wrap it the longer it will last in the freezer. If left unwrapped or poorly wrapped your sausage will be damaged by freezer burn, in a very short time. Vacuum sealing provides the best protection.