There are two methods for doing this.
- One is to edit the property in the prefab itself in the project window. This should propagate the changes to all prefabs that have not been overridden.
- The other method is to change the property in a single prefab. If you don't "apply" changes, that property will be considered "unique" and will override changes to the prefab. The title of the property will become bold.
If you "apply" the changes, that property will no longer be considered unique and all of the changes will be propagated to all prefabs except for properties that have been over-ridden in any given prefab.
USE OF PREFAB IN UNITY 3D
Prefabs are extremely useful in that they allow you to assign scripts/materials/other variables to a Game Object or hierarchy of Game Objects and keep them saved that way to be loaded at a later time. This makes it much easier to bring things into your game environment by letting you do all the work at once, save it to a prefab, and then just call that prefab whenever you like instead of having to reconstruct all the values again.