How to make mask effect

To create a mask effect need to have a layer that has to object that you are going to be masking. You need another layer with the object that will be masking you first layer's object. You go to modify in the menu bar then timeline and layer properties and set it to mask for the second layer. Then on the first layer you go to layer properties and set in to masked. While you play your movie you will notice the change form the beginning to the end.