There are different schools of thought when it comes to incubating. Depending on your incubator type, some people believe in a dry hatch. There is an excellent "sticky" under this forum explaining this method in detail. Other people believe in a low to moderate humidity for the first 18 days and then increasing the humidity for lockdown. Again, how much to increase the humidity is dependent on what type of incubator you are using and what school of thought you are following.
To increase humidity, you can add more water to the reservoirs (I slip a tube through the vent hole of the hovabator and pour a SMALL amount of water down into the water tray WITHOUT getting the eggs wet.) Do not use cold water. You can also put a wet sponge in the incubator. The idea of increasing humidity is to increase the surface area of the water.
To decrease humidity, you can remove some water, remove sponge, cover water with foil, or what I do is take a small plastic container with uncooked rice in it and place it in the incubator. The rice absorbs the extra moisture and you don't have to disturb the eggs. You can also make sure both vent holes are open.
Note that whatever changes you make, do them in small increments, because they could make a BIG difference in the temperature and humidity levels.
Ok, now if you tell us what kind of incubator you are using and maybe what kind of eggs you are using and what day you set them, we can help you further.
