Masking an exact shape


i feel like a noob…id like to mask an exact shape so i can do some cool animations that are only seen over that shape.


lets say i have a big letter ‘P’ that i made in photoshop and import it into flash. i made the background transparent and saved it as a .png file. so then i place a ‘P’ on stage that i want to be visible and i place another one directly on top of it to act as the mask. when i use set mask in this situation it doesnt use the shape of a ‘P’ is uses a box of some weird dimension.

anyone know a good way to do this?
should this work?