Page 232 - Photoshop for Lightroom Users – Scott Kelby 2nd Edition

image. So, if you want to crop those away, just grab the Crop tool (C) from the Toolbar and click-and-drag the outside edges of the cropping border inward
until the gaps fall outside that border. Click anywhere outside the cropping border (or hit Return [PC: Enter]) to lock in your crop (and, yes, it keeps your
two layers still intact).

Step Four:
Now, click on the top layer to make just that layer active, and then press-and-hold the Option (PC: Alt) key and click on the Add Layer Mask icon at the
bottom of the Layers panel (it’s the third icon from the left, circled here in red). This hides the top layer (the layer where she has no glasses on) behind a
black layer mask—that layer is still there, but it’s like it’s hidden behind a black wall. So, all you should now see is the glasses on with reflections image
(as seen here), and in the Layers panel, you’ll see that a black layer mask has been added to that top layer (that’s the black wall I was talking about).