Dry hatching is when you do not put any water in the incubator during incubation. Most people still add water when the eggs are due to actually hatch.
It works great for some people, poorly for others, and not at all for some.
Your local humidity determines whether it will work for you. If you live in a muggy swamp, "dry" hatching is probably fine, or you may even have to run a dehumidifier in the room with the incubator. If you live in a desert, you will probably need to add water to your incubator during incubation.
I would suggest you set up the incubator with no water, put in a hygrometer to measure humidity, and run it for a while. That will tell you if it's anywhere close to the right level. The humidity will probably be a little bit higher with eggs than when the incubator is empty, but running it empty will tell you if it's way too low or way too high.
