If your birds are laying and another imminent, they need layer feed or a container of free choice calcium source. Feeding chickens isn't difficult but birds in production need additional calcium in the form of layer feed or some large particle calcium source. They can quickly deplete available body stores.
I would never mix anything with chicken feed unless one is an expert in poultry nutrition. It is already complete for the age/type/sex of bird it was manufactured to feed.
This is especially true for oyster shell. It should be in a separate container. I keep a cage cup near the feed and another near the nest boxes. If it is mixed with feed, the chickens will have no choice whether to consume it or not. It will coat the feed and could possibly cause the chickens to consume up to 10% of their diet as calcium. That would be much too high for even a bird in full production.
There aren't dumb questions if someone has little experience on the topic.
Even those with experience should constantly reconsider their methods. Just because it has always worked doesn't mean it is perfectly correct.
