Page 146 - Photoshop for Lightroom Users – Scott Kelby 2nd Edition

Step Four:
To bring the image on the Background layer through to where we can fully see her again, double-click directly on the top layer’s thumbnail to bring up the
Blending Options in the Layer Style dialog. The reason why we want to be in this dialog is to use the Blend If options in the bottom center (shown here).
All you need to do here is drag the top right slider to the left and the image on the Background layer will be fully visible, as if it comes right through the
other image (as seen here). Click OK.