Resizing a masked image

Fairly new at PS (ok very new), and this seems like this should be such a simple thing. I have two layers, each with an image on it. On one layer it is a masked shape and all I want to do is resize it. I can't find any way to select and "stretch" it.

David,

Edit -> Free Trasnform (CTRL + T).

If you just want to modify the mask unlink it first in the layers pallet.