Select Free Transform from the Edit menu (CTRL+T on PCs). Move the shape over the top of the phone's screen.Ive stretched the shape using distortion (hold CTRL when dragging the corners), this helps to match the perspective, as you can line the bounding box up with the phones own vertices.It looks a little odd at the moment, so grab the central handles and size it down to roughly match the size of the screen.When you have it at the size you want, hit Enter or the Tick in the top toolbar to set it.I recommend saving the new shape's path at this point, again, it's useful if you need to replicate it later on.Select the Paths Tab on the Layer Palette and clicking the arrow in the corner. You can call it anything, but Heart would be descriptive.